AUTOMOTIVE  IGNITION  SYSTEMS 


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ENGINEERING   EDUCATION   SERIES 

AUTOMOTIVE 
IGNITION   SYSTEMS 


PREPARED    IN    THE 

EXTENSION  DIVISION  OF 
THE  UNIVERSITY  OF  WISCONSIN 

BY 

EARL  L.  CONSOLIVER,  M.E. 

SOMETIME   ASSISTANT   PROFESSOR  OP   MECHANICAL   ENGINEERING 
THE   UNIVERSITY   OP  WISCONSIN 

AND 

GROVER  I.  MITCHELL,  B.S. 

ASSISTANT   PROFESSOR   OF  MECHANICAL   ENGINEERING 
THE   UNIVERSITY   OF   WISCONSIN 


FIRST  EDITION 


McGRAW-HILL  BOOK  COMPANY,  INC. 

NEW  YORK:    370  SEVENTH  AVENUE 

LONDON:    6  &  8  BOUVERIE  ST.,  E.  C.  4 

1920 


9> 


COPYRIGHT,  1920,  BY  THE 
McGRAW-HiLL  BOOK  COMPANY,  INC. 


THE  MAPLE  I1  HESS  YORK  PA 


PREFACE 

Tins  volume  has  been  prepared  to  satisfy  the  demand  for  a  systematic 
course  of  study  dealing  with  the  ignition  systems  used  on  automobiles, 
trucks,  tractors,  and  airplanes.  In  preparing  the  text  the  authors  have 
had  in  mind  the  needs  of  the  men  who  have  to  install,  adjust,  and  repair 
ignition  systems  in  the  factory  and  repair  shop,  as  well  as  the  needs  of 
the  automobile  owner  who  desires  a  better  understanding  of  the  principles 
and  construction  of  the  modern  ignition  system.  A  few  systems  have 
been  included  which  are  no  longer  manufactured  but  many  of  which  are 
still  to  be  found  in  operation. 

The  authors  wish  to  express  their  appreciation  of  the  help  and  construc- 
tive criticism  of  Professor  Ben  G.  Elliott;  the  help  of  Mr.  Lawrence  E.  Blair 
in  the  preparation  of  many  of  the  drawings ;  and  the  cooperation  of  many 
of  the  manufacturers  of  the  equipment  described. 

THE  UNIVERSITY  OF  WISCONSIN,  G.  I.   M. 

MADISON,  WISCONSIN.  E    L    C 

October  1,  1920. 


434155 


CONTENTS 

PAGE. 

PREFACE    ........*.....    .    .  y 

CHAPTER  I.     PRINCIPLES  OF  ELECTRICITY  AND  MAGNETISM 
ART. 

1.  Electricity 1 

2.  Hydraulic  Analogy  of  the  Electric  Current 1 

3.  Conductors  and  Non-conductors      '......  2 

4.  Resistance -...........' 2 

5.  Effect  of  Temperature  on  Electrical  Resistance 4 

6.  Relation  between  Current,  Voltage,  and  Resistance 4 

7.  Series  Circuits . 6 

8.  Parallel  Circuits  .    .    .    .    .    .    .    .    ...  ...    .    .    .    .    .    ...........  6 

9.  Electrical  Power      ........    t 8 

10.  Effects  of  Electric  Current ." .  8 

11.  Magnetism d 

12.  Natural  and  Artificial  Magnets 9 

13.  Magnetic  and  Non-magnetic  Metals 10 

14.  The  Poles  of  a  Magnet  .    .......................  10 

15.  The  Magnetic  Field V.,..    .^  ..............  12 

16.  Electron!  agnetism 12 

17.  The  Electromagnet     .......    v 14 

18.  To  Determine  the  Polarity  of  an  Electromagnet .    .    .  14 

19.  Electromagnetic  Induction    .    . ,    .    .  . ;    .    .    .  15 

CHAPTER  II.     IGNITION  BATTERIES 

20.  Primary  and  Secondary  Batteries    .....' 19 

21.  The  Dry  Cell .    <- .    .    .  20 

22.  Testing  Dry  Cells *  .    .    .    .    .    .......    .^  ,  V  .-    .    .  22 

23.  Wiring  of  Ignition  Batteries ...........  23 

24.  Care  of  Dry  Cells  ..............    .    .    ,   .    .  '.    .  ";    ...  25 

25.  Storage  Cells ,:    .    .    .    .    .    .....  '.  '.    .    .    .:  .    .    .  25 

26.  The  Edison  Storage  Battery.    .    :    .    .    .    .    .    .    ,    .\    .    .    .    /.    .    .    .    .  25 

27.  The  Lead  Storage  Battery     .....'.........    .    .    .    .    .>  .    .  27 

28.  Separators 31 

29.  The  Electrolyte ................' 33 

30.  The  Hydrometer .    , 34 

31.  Action  of  the  Lead  Storage  Cell  on  Discharge 35 

32.  Action  of  the  Lead  Storage  Cell  on  Charge 36 

33.  Heat  Formed  on  Charge  and  Discharge     , 36 

34.  Evaporation  of  Water 37 

35.  Necessity  of  Adding  Pure  Water 37 

36.  Storage  Battery  Testing 37 

37.  Variations  in  Cell  Readings 38 

vii 


viii  CONTENTS 

ABT.  PAGE 

38.  Variation  in  Hydrometer  Readings  Due  to  Temperature  Changes    ....  39 

39.  Capacity  of  a  Storage  Battery 40 

40.  Battery  Charging 41 

41.  Detailed  Instructions  for  Battery  Charging 42 

42.  Sulphation 44 

43.  Effect  of  Overfilling 46 

44.  Corroded  Terminals 46 

45.  Disintegrated  and  Buckled  Plates 47 

46.  Sediment 48 

47.  Care  of  Storage  Batteries  in  Winter 49 

48.  Conditions  Causing  the  Battery  in  the  Electrical  System  to  Run  Down  .    .  49 

CHAPTER  III.     THE  JUMP-SPARK  IGNITION  SYSTEM 

49.  Requirements  of  Automotive  Engine  Ignition   .    . 51 

50.  Make-and-break  and  Jump-spark  Ignition 52 

51.  The  Low-tensio'n  Coil  for  Make-and-break  Ignition . 52 

52.  The  Induction  Coil     .    .    .    .    .    .    .    .    ....    .... 53 

53.  Coil  Impregnation  ................ 55 

54.  Operation  of  the  Simple  Jump-spark  Ignition  System 56 

55.  The  Condenser    .    . 57 

56.  The  Safety  Gap  .    ...    .    .    .    .    .    .    .-."'..    .'.    .    .    .    ?   V 59 

57.  Spark  Plugs ...    .    .;.    .    ....    ..^.  :.    ..'-.' 59 

58.  The  Vibrating  Induction  Coil 64 

59.  The  Three-terminal  Coil 65 

60.  The  Vibrating  Type  Ignition  System     .    .    .    :    .    .' -^..'  .«  . 65 

61.  Timers .    .    .    .    .    ',    '. 66 

62.  Master  Vibrators     .........    . 67 

63.  Spark  Advance  and  Retard   .    .    .    .    ....    ..  .    .-. 69 

64.  Principles  of  Ignition  Timing 69 


CHAPTER  IV.     MODERN  BATTERY  IGNITION  SYSTEMS 

65.  Construction  of  a  Typical  Battery  Ignition  System 73 

66.  The  Breaker 75 

67.  The  Distributor       ; 76 

68.  The  Resistance  Unit 77 

69.  Effect  of  the  Resistance  Unit  upon  Ignition 77 

70.  Automatic  and  Manual  Spark  Advance 78 

71.  The  Atwater-Kent  Ignition  System,  Type  K-2 79 

72.  The  Atwater-Kent  Ignition  System,  Type  CC      . 84 

73.  The  Connecticut  Battery  Ignition  System 88 

74.  The  Remy  Ignition  System 94 

75.  The  Remy-Liberty  Ignition  Breaker  for  U.  S.  Military  Truck,  Class  B .    .    .  98 

76.  The  North  East  Battery  Ignition  System 98 

77.  The  Delco  Ignition  System 101 

78.  The  Westinghouse  Ignition  Systems 103 

79.  The  Philbrin  Ignition  System   ...        107 

80.  Wagner  Ignition  System Ill 

80- A.  Timing  Battery  Ignition  with  the  Engine 115 

81.  Care  of  Battery  Ignition  Systems 116 


CONTENTS  ix 

CHAPTER    V.     BATTERY    IGNITION    SYSTEMS   FOB   MULTIPLE   CYLINDER   ENGINES 

ART.  PAGE 

82.  Firing  Order  of  Four- and  Six-cylinder  Engines "....117 

83.  Firing  Order  of  Eight-cylinder  Engines 119 

84.  Determining  the  Firing  Order  of  an  Eight-cylinder  Engine 121 

85.  The  Delco  Ignition  System  for  the  Oldsmobile  Eight 121 

86.  The  Delco  Ignition  System  for  the  Cadillac  Eight    .    .    .    .    .-.    I    ...    .    122 

87.  Firing  Order  of  Twelve-cylinder  Engines ..,,...".    .    127 

88.  The  Delco  Ignition  System  for  the  Packard  Twin  Six.    .    ..  ..  V.  .    .    ...    .    129 

89.  Delco  Ignition  for  Pierce- Arrow  Dual  Valve  Six ,    '-.    .    .    .    .    132 

90.  Ignition  Requirements  of  Liberty  Twelve  Aircraft  Engines    .    .  • 135 

91.  The  Delco  Ignition  System  for  Liberty  Twelve  Aircraft  Engines  .  .'.'•  '.    .    .    136 

92.  Ignition  Timing  on  Eight- and  Twelve-cylinder  Engines .    .    141 

CHAPTER  VI.     THE  LOW-TENSION  MAGNETO 

93.  Magneto  Classification. .........  v    .  T ..  143 

94.  Magneto  Magnets. ',.    .    .  V   •    •    •  143 

95.  Lines  of  Force. .    .    .    .     .    .......    ....    .  144 

96.  Types  of  Magnets .,.,;..,.;..,.  144 

97.  Mechanical  Generation  of  Current 145 

98.  Low- and  High-tension  Magnetos ........  146' 

99.  Armature  and  Inductor  Type  Magnetos 147 

100.  Current  Wave  from  a  Shuttle  Wound  Armature 147 

101.  Magneto  Speeds 148 

102.  Low-tension  Magneto  Ignition  System  with  Interrupted  Primary  Current  .  149 

103.  Low-tension  Magneto  Ignition  System  with  Interrupted  Shunt  Current.     .  150 

104.  Dual  Ignition  Systems 152 

105.  Splitdorf  Low-tension  Dual  Ignition  System  with  Type  T  Magneto     ...  153 

106.  Remy  Inductor  Type  Magneto     .    .''.',;  ri.  .'.- '..    .    .    .    .  154 

107.  The  Ford  Ignition  System *-...    .    .'.    .   .    .    . -,    .    .  157 

108.  Timing  the  Ford  Ignition  System .    .    .    .    .    .    .  160 

CHAPTER  VII.     MODEEN  HIGH-TENSION  MAGNETOS — ARMATURE  TYPES 

109.  The  High-tension  Magneto ...../..    ....    .    16i 

110.  The  Bosch  High-tension  Magneto   .    .    .    .    .    .    .    „   .    .    ..,,-..,..    .    161 

111.  The  Bosch  High-tension  Dual  Ignition   .    .    .    ....    .    .....    .'.,  ,    .    170 

112.  The  Bosch  High-tension  Magneto,  Type  NU4  .    .    .    .    .:  .    .    .    .   ,.  v  .    .    173 

113.  Timing  the  Bosch  Magneto,  Type  NU4 175 

114.  The  Eisemann  High-tension  Magneto,  Type  G4 176 

115.  The  Eisemann  High-tension  Dual  Magneto,  Type  GR4 181 

116.  Timing  of  the  Eisemann  Magneto  to  the  Engine  for  Variable  Spark     .    .    .    185 

117.  The  Eisemann  Magneto  with  Automatic  Spark  Advance 185 

118.  Eisemann  Impulse  Starter 187 

119.  Simms  High-tension  Dual  Ignition  System    .    .    . .188 

120.  The  Berling  High-tension  Du?l  Magneto   .    .    ; 190 

121.  The  Kingston  Model  O  High-tension  Magneto 192 

122.  The  Mea  Magneto 194 

CHAPTER  VIII.  MODERN  HIGH-TENSION  MAGNETOS — INDUCTOR  TYPES 

123.  Principles  of  the  Inductor  Type  Magneto 197 

124.  The  K-W  High-tension  Magneto 198 


x  CONTENTS 

ABT.  PAGE 

125.  The  Dixie  Magneto  for  Four-  and  Six-cylinder  Engines 205 

126.  The  Splitdorf  Aero  Magneto 209 

127.  The  Splitdorf  Aero  Magneto  with  Impulse  Starter 214 

128.  The  Aero  Magneto  with  Battery  Starting  Connections 216 

129.  The  Aero  Magneto  for  Eight-cylinder  Engines 217 

130.  The  Aero  Magneto  for  Twelve-cylinder  Engines       219 

131.  The  Aero  Airplane  Magneto 219 

132.  Aero  Magneto  Adjustments 222 

CHAPTER  IX.     CARE  AND  REPAIR  OF  IGNITION  APPARATUS 

133.  Methods  of  Mounting  Ignition  Apparatus '••••'. 225 

134.  Magneto  Couplings ..." 229 

135.  Bearings  and  Lubrication 230 

136.  Impulse  Starters • >    .    .  ..  V.    . ••'• . . -.. 232 

137.  General  Rules  for  Magneto  Timing ;  ' 232 

138.  General  Rules  for  Battery  Ignition  Timing    .    .    . 235 

139.  Care  and  Adjustment  of  Breakers  and  Timers.     ...-..' 236 

140.  Wiring  and  Terminals    ....    ....    .    .'.'-.    .    . 238 

141.  Wiring  the  High-tension  System.     .-  v   ...    .    .... 241 

142.  Testing  High-tension  Insulation,      .    .    .    ...    .-....' 242 

143.  Care  of  the  Distributor ,   ...... .242 

144.  Installation  and  Care  of  Spark >Plugs. 243 

145.  Spark  Plug  Testing : -.    ;   '.    .    ;.. 244 

146.  Ignition  Coil  Testing      .'.-.--  .   ,    ,    / 245 

147.  Condenser  Troubles  and  Method  of  Testing. 247 

148.  Recharging  Magnets 249 

CHAPTER  X.     IGNITION  TROUBLES  AND  REMEDIES 

149.  Starting  the  Engine .    .--...< 255 

150.  Failure  of  the  Engine  to  Start      ...........'........  255 

151.  Testing  the  Battery  Ignition  System 255 

152.  Testing  the  Magneto  Ignition  System     .    .    ;    .    ;    .    .    ."_ 256 

153.  Locating  a  Misfiring  Cylinder V 256 

154.  Defective  Spark  Plugs 256 

155.  Defective  Wiring  and  Ignition  Apparatus 257 

156.  Battery  Ignition  Breaker 258 

157.  Defective  Condenser  .    .    .    . 258 

158.  The  Resistance  Unit .' 258 

159.  Coil  Adjustments 259 

160.  Breakdown  of  Coil  Wiring  or  Insulation 259 

161.  Timers 259 

162.  Improper  Spark  Timing 259 

163.  Dry  Batteries .'....' 260 

164.  Storage  Batteries     .    .    .... 260 

165.  Magneto  Troubles  .    .  ..    , 260 

166.  Premature  Ignition 261 

167.  Effects , of  Faulty  Ignition  on  Engine  Operation 261 

168.  Things  to  Remember  Regarding  Ignition 262 

INDEX  .  263 


AUTOMOTIVE  IGNITION  SYSTEMS 

CHAPTER  I 
PRINCIPLES  OF  ELECTRICITY  AND  MAGNETISM 

1.  Electricity. — Probably  no  other  factor  has  played  such  an  import- 
ant part  in  making  possible  the  modern  gasoline  automobile  with  its  four-, 
six-,  eight-,  or  twelve-cylinder  engine  than  has  electricity  in  its  many 
applications.     It  may  be  said  that  the  perfection  of  the  modern  auto- 
motive power  plant  has  been  brought  about  largely  by  the  development 
of  the  electrical  equipment.     Electricity,  in  addition  to  igniting  the  fuel 
charge  within  the  engine  cylinders,  is  also  called  upon  to  start  the  engine, 
furnish  the  light,  operate  the  horn,  and,  in  some  instances,  operate  cigar 
lighters  and  hand  warmers,  preheat  the  fuel  charge  for  cold  weather 
starting,  and  shift  the  gears  of  the  'transmission.     That  electricity  is 
indispensable  in  the  automotive  field  is  evidenced  by  the  fact  that  prac- 
tically all  makes  of  passenger  automobiles,  as  well  as  many  trucks  and 
tractors,  are  completely  equipped  with  electric  starting,  lighting,  and 
ignition  systems. 

Since  the  successful  operation  of  the  automobile  depends  so  greatly 
upon  its  electrical  equipment,  it  is  essential  that  this  equipment  be 
operated  properly  and  kept  in  the  best  of  adjustment  and  repair.  In 
order  that  this  may  be  done  successfully,  it  is  necessary  that  a  clear 
understanding  be  had  of  the  fundamental  electrical  and  electromagnetic 
principles  underlying  the  construction  and  operation  of  the  electrical 
equipment  used.  The  exact  nature  of  electricity  is  not  known;  but  its 
effects,  the  laws  governing  its  action,  and  the  methods  of  controlling  it 
and  using  it  for  doing  various  kinds  of  work  are  well  understood. 

The  electric  current  used  in  the  electrical  equipment  on  the  automo- 
bile may  be  generated  in  either  of  two  ways.  One  of  these  is  by  chemical 
action,  the  principle  employed  in  batteries,  and  the  other  is  by  the  con- 
version of  mechanical  energy  into  electrical  energy  by  means  of  electro- 
magnetic induction.  This  is  the  method  used  in  the  magneto  and  in  the 
generator. 

2.  Hydraulic  Analogy  of  the  Electric  Current. — An  electric  current 
flowing  through  a  wire  may  be  compared  to  a  stream  of  water  flowing 
through  a  pipe.     Just  as  water  will  flow  through  a  pipe,  due  to  pressure 
from  a  pump  or  a  difference  in  level,  such  as  from  A  to  B  in  Fig.  1,  so 

1 


c  c  ^AUTOMOTIVE  IGNITION  SYSTEMS 


B 

i 

-*> 

h 



J  ^ 

jfc-~- 

—  ~~1E^ 

^ 

electric  current  will  flow  through  a  conductor,  due  to  an  electrical  pressure 
or  potential  created  by  a  battery  or  a  mechanically  driven  generator.  For 
example,  if  a  wire  is  connected  to  the  two  terminals  of  a  storage  battery, 
as  in  Fig.  2,  a  current  will  flow  through  the  wire  from  the  high  potential 
or  positive  (+)  terminal  to  the  low  potential  or  negative  (  — )  terminal 
as  indicated  by  the  arrows.  The  pressure  causing  the  water  to  flow  is 
measured  in  pounds  per  square  inch  and  the  rate  of  flow  in  gallons  per 
unit  of  time,  while  in  the  electric  circuit  the  pressure  or  electromotive 

force  is  measured  in  units 
called  volts  and  the  rate  of 
current  flow  in  amperes. 

3.  Conductors  and  Non- 
conductors.— All  substances 
conduct  electricity  to  some 
extent,  some  much  better 

F,o.  l.^Hydraulic  analogy  of  electric  current.        than     othf S'      Tbet^.    » J  n° 

known  substance  which  does 

not  offer  some  resistance  to  the  flow  of  electric  current  through  it. 
Materials  such  as  silver,  copper,  etc.,  which  offer  a  comparatively  low 
resistance,  are  known  as  conductors,  while  materials  such  as  porcelain, 
glass,  fiber,  rubber,  etc.,  which  offer  a  high  resistance  to  the  passage  of 
current,  are  known  as  non-conductors  or  insulators.  Liquids  which  offer 
a  low  resistance  to  the  passage  of  current  are  known  as  eiectroiytes,  while 
liquids  which  offer  a  high  resistance 
are  known  as  non-electrolytes. 

4.  Resistance. — The  opposition 
which  a  substance  offers  to  the  pas- 
sage of  an  electric  current  through 
it  is  the  resistance  of  that  substance, 
and  the  unit  of  this  electrical  resist- 
ance is  called  the  ohm.  The  ohm 
may  be  defined  as  the  resistance  of 
a  circuit  in  which  one  ampere  of 
current  flows  under  one  volt  pres- 
sure. The  resistance  of  a  circuit 
may  be  compared  to  the  friction 
offered  by  a  pipe  to  the  flow  of  a  liquid,  in  that  the  electrical  resistance 
of  the  circuit  depends  upon  the  size,  Length,  material,  and  temperature  of 
the  conductor,  just  as  the  flow  of  any  liquid  is  resisted  by  friction  which 
in  turn  depends  upon  the  size  and  length  of  the  pipe,  the  material  or 
kind  of  pipe  (whether  smooth,  rough,  straight,  or  crooked),  and  upon  the 
temperature  of  the  liquid.  Thus  it  is  evident  that  the  size  of  a,  certain 
wire  determines  the  amount  of  current  it  can  carry  at  a  given  voltage 
without  excessive  heating.  A  small  wire  can  naturally  conduct  a  small 


FIG.  2. — -Battery  electric  circuit. 


PRINCIPLES  OF  ELECTRICITY  AND  MAGNETISM 


RESISTANCE  OF  STANDARD  ANNEALED  COPPEP  WIRE,  AMERICAN  WIRE  GAGE  (BROWN 

&  SHARPE) 


Gage  No. 
(B.  &  S.) 

Actual  diam. 
of  wire  in 
inches 

Nominal 
diam.  inches 

Feet  per 
pound 
(bare  wire) 

Ohms  per  1,000  feet 

20  deg.  Cent. 
(  =  68  deg. 
Fahr.) 

50  deg.  Cent. 
(=  122  deg. 
Fahr.) 

0000                    0.4600 

%                     1.561          0.04901 

0.05479 

000                    0.4096 

!%2                     1.968'         0.06180 

0.06909 

00 

0.3648              2%4 

2.482 

0.07793 

0.08712 

0 

0.3249 

2><34 

3.130 

0.09827 

0.1099 

1 

0.2893 

l*4 

3.947 

0.1239 

0.1385 

2 

0.2576 

X 

4.977 

0.1563 

0.1747 

3 

0.2294 

%2 

6.276 

0.1970 

0.2203 

4 

0.2043 

1X* 

7.914 

0.2485 

0.2778 

5 

0.1819 

. 

9.980 

0.3133 

0.3502 

6 

0.1620 

K* 

12.58 

0.3951 

0.4416 

7 

0.1443 

.  . 

15.87 

-0.4982 

0.5569 

8 

0.1285 

X 

20.01 

0.6282 

0.7023 

9 

0.1144 

K* 

25.23 

0.7921 

0.8855 

10 

0.1019 

.  .  . 

31.82 

0.9989 

1.117 

11 

0.0907 

%2 

40.12 

1.260 

1.408 

12 

0.0808 

%* 

50.59 

1.588 

1.775 

13 

0.0719 

.  .  . 

63.80 

2.003 

2.239 

14 

0.0641 

Ke 

80.44 

2.525 

2.823 

15 

0.0571 

101.4 

3.184 

3.560 

16 

0.0508 

%4                 127.9 

4.016 

4.489 

17 

0.0453 

161.3 

5.064 

5.660 

18 

0.0403 

203.4 

6.385 

7.138 

19 

0.0359 

256.5 

8.051 

9.001 

20 

0.0320 

Mz                323.4 

10.15 

11.35 

21 

0.0285 

407.8 

12.80 

14.31 

22 

0.0253 

514.2 

16.40 

18.05 

23 

0.0226                ...                  648.4 

20.36 

22.76 

24 

0.0201                ...                  817.7 

25.67 

28.70 

25 

0.0179                ...               1,031.0 

32.37 

36.18 

26 

0.0159               >^4              1,300.0 

40.81 

45.63 

27 

0.0142 

1,639.0 

51.47 

57.53 

28 

0.0126 

2,067.0 

64.90 

72.55 

29 

0.0113 

2,607.0 

81.83 

91.48 

30 

0.0100 

3,287.0 

103.2 

115.4 

31 

0.0089 

4,145.0 

130.1 

145.5 

32 

0.0080 

5,227.0 

164.1 

183.4 

33 

0.0071 

6,591.0 

206.9 

231.3 

34 

0.0063 

8,310.0 

260.9 

291.7 

35 

0.0056 

10,480.0 

329.0 

367.8 

36 

0.0050 

13,210.0 

414.8 

463.7 

37 

0.0045 

16,660.0 

523.1 

584.8 

38 

0.0040                ...             21,010.0 

659.6 

737.4 

39 

0.0035                ...             26,500.0 

831.8             929.8 

40 

00031                ...             33,410.0 

1,049.0          1,173.0 

4  AUTOMOTIVE  IGNITION  SYSTEMS 

current,  while  it  requires  a  large  wire  to  conduct  a  large  current  at  the 
same  pressure,  just  as  it  requires  a  large  pipe  to  conduct  a  large  flow 
of  water.  In  fact,  it  has  been  found  that  the  resistance  of  a  conductor 
is  directly  proportional  to  its  length  and  inversely  proportional  to  its  cross- 
sectional  area. 

The  resistance  of  a  conductor  depends  not  only  upon  its  size  and 
length,  but  also  upon  the  kind  of  metal  of  which  it  is  composed,  since 
some  metals  are  much  better  conductors  than  others.  For  instance, 
silver  is  a  better  conductor  than  copper,  copper  is  much  better  than 
iron,  and  iron  is  much  better  than  lead.  Owing  to  the  relative  cheapness, 
low  resistance,  and  high  breaking  strength  of  copper,  it  is  recognized  as 
the  best  all-round  commercial  conductor;  consequently,  it  is  used  uni- 
versally in  the  construction  and  wiring  of  automobile  electrical  equip- 
ment. The  resistance  of  different  sizes  of  annealed  copper  wire  is  given 
in  the  table  on  p.  3.  From  this  table  it  will  be  noted  that  the  re- 
sistance increases  as  the  size  of  the  wire  decreases  and  increases  with  an 
increase  in  temperature.  The  change  in  resistance  due  to  an  increase  in 
temperature  can  readily  be  seen  by  comparing  the  last  two  columns  of 
the  table. 

5.  Effect  of  Temperature  on  Electrical  Resistance.  —  With  the  excep- 
tion of  certain  metal  alloys,  the  resistance  of  practically  all  substances 
varies  with  a  change  in  temperature.     It  has  been  found  that  in  the  case 
of  all  metal  conductors  used  on  the  automobile,  such  as  platinum,  tung- 
sten, copper,  lead,  iron,  etc.,  an  increase  in  temperature  is  accompanied 
by  an  increase  in  electrical  resistance,  while  in  the  case  of  insulating 
materials,  carbon  and  various  electrolytic  solutions,  an  increase  in  tem- 
perature is  accompanied  by  a  decrease  in  resistance.     These  character- 
istics are  important  to  remember  in  connection  with  the  operation  of 
the  ignition  resistance  unit,  spark  plugs,  carbon  brushes,  storage  battery 
electrolyte,  and  other  parts  of  the  electrical  system. 

6.  Relation  between  Current,  Voltage,  and  Resistance.  —  It  was  dis- 
covered by  Ohm  that  in  the  case  of  circuits  which  carry  current  continu- 
ously in  one  direction  (known  as  direct-current  circuits)  ,  a  definite  relation 
exists  between  the  resistance  of  a  circuit  and  the  current  which  will  flow 
under  a  certain  voltage.     This  relation  is  known  as  Ohm's  law  and  may 
be  stated  as  follows:  The  current  strength  in  any  circuit  is  directly  pro- 
portional to  the  voltage  applied  to  the  circuit  divided  by  the  resistance  of  the 
circuit.     This  law  is  usually  expressed  as:  Current  equals  voltage  divided 
by  resistance,  or,  stating  the  same  thing  in  another  way, 

Volts  E 


in  which  I  =  the  current  in  amperes,  E  =  the  voltage  in  volts,  and  R  = 
the  resistance  in  ohms. 


PRINCIPLES  OF  ELECTRICITY  AND  MAGNETISM 


The  formula  for  Ohm's  law  may  also  be  transposed  into  other  forms 
convenient  for  finding  the  voltage  and  resistance,  namely: 


and 


Volts  =  amperes  X  ohms  or  E  =  IR 

~,  Volts          D      E 

Ohms  =  -T—        -  or  R  =  -=- 

Amperes  / 


(2) 


,0. 

(3) 


Thus  if  the  voltage  and  resistance,  or  the  current  and  resistance,  or 
the  voltage  and  current  are  known,  the  exact  relation  between  the  vol- 

AMMETER 


TERMINALS 

CONNECTED 

SOURCE  OF 


CURRENT  SUPPLY 


TO 


FIG.  3. — Method  of  connecting  ammeter  and  voltmeter  on  electric  circuit. 

tage,  current,  and  resistance  can  be  readily  calculated  by  applying  the 
proper  formula. 

The  voltage  and  current  of  a  circuit  can  be  readily  measured  by  con- 
necting a  voltmeter  and  an  ammeter,  respectively,  as  shown  in  Fig.  3. 
Although  the  two  instruments  are  usually  very  similar  in  external  ap- 
pearance, the  voltmeter  is  designed  to  measure  the  electrical  pressure  in 
volts  and  is  connected  across  the  source  of 
current  supply,  such  as  terminals  A  and  B, 
Fig.  3,  while  the  ammeter  is  an  instrument 
for  measuring  the  current  flow  in  amperes 
and  is  connected  in  the  circuit,  Fig.  3,  so 
that  all  the  current  flowing  in  the  circuit 
passes  through  the  instrument.  The 
ammeter  is  the  only  one  of  the  two  in- 
struments usually  furnished  on  the  auto- 
mobile, the  voltmeter  being  used  chiefly 
for  testing  purposes.  The  ammeter  is 
usually  of  the  type  shown  in  Fig.  4.  It 
is  located  on  the  instrument  board  and  is  FlG- 
connected  in  the  lighting  and  battery 
charging  circuits  so  'that  it  will  indicate  the  amount  of  current  either 
charging  the  battery  or  discharging  from  the  battery. 

As  there  is  no  instrument  for  measuring  directly  the  electrical  resist- 
ance of  a  circuit,  this  must  be  calculated  by  first  measuring  the  voltage 
and  current  as  just  described  and  dividing  the  voltage  in  volts  by  the 
current  in  amperes  as  in  formula  (3).  A  practical  application  of  this 
formula  may  be  seen  in  the  determination  of  the  resistance  of  a  coil  of 


6  AUTOMOTIVE  IGNITION  SYSTEMS 

wire  connected  across  the  terminals  of  a  6-volt  battery  and  drawing  a 
current  of  2  amperes.  The  resistance  of  the  coil  will  be  equal  to  6  volts 
divided  by  2  amperes,  or  3  ohms. 

If  this  same  coil  of  wire  were  connected  across  a  12-volt  battery,  the 
current  which  it  would  draw  would  be  according  to  formula  (1),  12  volts  di- 
vided by  3  ohms,  or  4  amperes,  or  twice  the  amount  drawn  from  the  6- 
volt  battery. 

When  a  wire  consists  of  such  material,  size,  length,  and  temperature 
as  to  offer  1  ohm  resistance,  the  voltage  required  to  force  1  ampere  through 
it,  according  to  formula  (2),  must  be  1  volt.  Thus  it  will  be  seen  that 
the  volt  or  unit  of  electrical  pressure  may  be  defined  as  the  pressure  required 
to  force  a  current  of  one  ampere  through  a  circuit  having  one  ohm  resistance. 

7.  Series  Circuits. — When  two  or  more  electrical  devices  or  circuits 
are  connected  so  that  the  same  current  flowing  through  one  must  also 
flow  through  the  others,  such  as  Ri  and  R»,  Fig.  5,  they  are  said  to  be  in 
series  and  the  circuit  is  called  a  series  circuit.  The  resistance  of  the  en- 
tire circuit  is  the  total  sum  of 

SWITCH  .-,  .   ,  f          , 

-•  _  the  resistances  of  each  circuit. 


For  example,  if  Ri  and  Rz,  Fig. 
5,  represent  two  6-volt  lamps 
LAMPS  connected  in  series,  the  filament 
of  each  being  of  such  material, 
size,  and  length  as  to  offer  2 

P.O.  S.-Lamps  connected  in  series.  °hmS  ^sistance,  the  total  resist- 

ance  offered  by  the  lamps  will 

be  Ri  plus  R2,  or  2  +  2  =  4  ohms.  The  current  which  the  lamp  circuit 
will  draw  from  a  6-volt  battery  will  then  be  according  to  formula  (1), 

E        6 
/  =    ft    =  4  =  1J£  amperes. 

If  the  lamps  connected  in  this  manner  are  both  of  the  same  kind,  for 
example,  6-volt,  18  candlepower,  each  will  burn  at  one-half  voltage, 
and,  consequently,  at  a  correspondingly  reduced  brilliancy. 

8.  Parallel  Circuits. — When  two  or  more  circuits  are  connected  to 
the  same  source  of  current  supply,  thus  providing  more  than  one  path  for 
the  current  to  flow,  as  in  Fig.  6,  the  circuits  are  said  to  be  connected  in 
parallel.  It  is  evident  that  the  more  paths  there  are  for  the  current  to 
travel  in,  the  less  will  be  the  total  resistance  and  the  greater  will  be  the 
current  flowing  in  the  entire  circuit.  It  will  also  be  seen  that  the  amount 
of  current  flowing  in  each  parallel  circuit  will  be  in  proportion  to  the 
resistance  of  that  circuit.  For  example,  if  two  circuits  are  connected  in 
parallel,  as  in  Fig.  7,  having  10  ohms  and  1  ohm  resistance,  respectively, 
the  current  flowing  in  the  two  circuits  will  be  in  proportion  to  the  resist- 
ances of  the  two  circuits  or  a  ratio  of  10  to  1.  Thus  if  a  total  current  of 


PRINCIPLES  OF  ELECTRICITY  AND  MAGNETISM 


11  amperes  is  flowing  through  the  two  circuits,  the  10  ohm  circuit  will 
conduct  1  ampere,  and  the  1  ohm  circuit  10  amperes. 


SWITCH 


FIG.  6. — Lamps  connected  in  parallel. 

The  total  resistance  of  two  or  more  parallel  circuits  may  be  determined 
from  the  following  formula: 

*•-!     i     i—  r  <4> 

P~  +   7?    +   B '    +   P  '  +    etC' 
KI       n>2       JKs       K± 

in  which  RI,  R2,  RA)  etc.  represent  the  resistances  of  the  various  circuits 
connected  in  parallel.     As  an  example,  assume  that  tfye  lamps  RI,  R?,  and 

SWITCH 


R=IO  OH 


=l  OHM 


FIG.  7. — Parallel  circuits. 

Ra  in  Fig.  6  have  a  resistance  of  8,  4,  and  2  ohms,  respectively;  then  by 
formula  (4)  the  combined  resistance  of  the  three  lighting  circuits  will  be, 

1  18 

R  =  -T- — ^ 1  =  »  =  =,  or  1.143  ohms. 

842      8 

The  total  current  drawn  by  all  the  lamps,  if  connected  to  a  6-volt 
storage  battery,  as  shown,  can  now  be  found  by  formula  (1), 

E          6 
/  =  jyor  T^IQ  =  5.25  amperes. 

£\j  1 .  ITCO 

By  connecting  the  lamps  in  parallel,  each  lamp  will  operate  at  the 
same  voltage  (the  voltage  of  the  battery)  and  independent  of  the  other 
lamps  so  that  if  one  lamp  is  turned  off,  or  burned  out,  the  other  lamps 


8  AUTOMOTIVE  IGNITION  SYSTEMS 

will  not  be  affected,  but  will  continue  to  burn  with  full  brilliancy.  This, 
however,  would  not  be  the  case  if  the  lamps  were  connected  in  series  as 
in  Fig.  5,  since  the  burning  out  of  one  lamp  would  "open"  the  entire 
circuit  and  prevent  the  current  from  flowing  through  the  other  lamp. 

9.  Electrical  Power.  —  The  unit  of  electrical  power  is  the  watt  which 
may  be  defined  as  the  rate  at  which  work  is  performed  by  a  current  of  1 
ampere  flowing  through  a  circuit  under  1  volt  pressure.  Expressing  this 
as  a  formula: 

P  =  E  X  I  (5) 

in  which  E  =  the  voltage  in  volts,  I  =  the  current  in  amperes,  and  P 
=  the  power  in  watts. 

Thus  it  will  be  seen  that  if  the  voltage  and  current  in  a  circuit 
are  known,  the  electrical  power  in  watts  may  be  readily  determined  by 
multiplying  the  voltage  in  volts  by  the  current  in  amperes.  If  the  prim- 
ary circuit  of  an  automobile  ignition  system  draws  a  continuous  current 
of  2~^2  amperes  from  a  6-volt  battery  (as  indicated  by  the  dash  ammeter) 
the  electrical  power  or  work  required  of  the  battery  will  be  P  =  E  X  /, 
or  6  X  2^  =  15  watts. 

In  many  instances  the  watt  is  too  small  a  unit  for  convenient  use; 
consequently,  the  kilowatt  (kw.)  or  1,000  watts  is  frequently  used.  It 
requires  746  watts  to  equal  1  mechanical  horsepower  (hp.);  therefore, 

1000  (watts  in  1  kw.) 
1  kw.  =    f7Aaf  ,  ,     x  or  1.34  hp. 

746(wattc^m  1  hp.) 

and 

746  (watts  in  1  hp.) 
1  hp.  =  -1Ann/        —r*  —  ^rr\  or  .746  kw. 
1000  (watts  in  1  kw.) 


Approximately,  1  kilowatt  equals  IJ^  horsepower,  and  conversely,  1 
horsepower  equals  %  kilowatt.  These  figures,  representing  the  relation 
between  mechanical  and  electrical  power,  will  be  found  very  necessary 
in  calculating  the  power  requirements  of  motors  and  generators;  conse- 
quently, it  is  advisable  that  they  be  memorized.  It  should  also  be 
remembered  that, 

1  kilowatt  of  power  used  for  1  hour  =  1  kilowatt  hour  (kw.  hr.)  and 
1  ampere  of  current  used  for  1  hour  =  1  ampere  hour  (amp.  hr.) 
10.  Effects  of  Electric  Current.  —  Experiments  have  shown  that  an 
electric  current  in  flowing  through  certain  circuits  produces  various 
physical,  chemical,  and  magnetic  changes  or  effects.     On  the  automobile, 
these  effects  include  (1)  heat  and  light,  as  witnessed  in  the  glow  of  the  lamp 
filaments;  (2)  chemical  action,  which  is  the  principle  of  the  storage  battery; 
and  (3)  magnetism,  upon  which  the  induction  coil,  magneto,  generator, 
and  starting  motor  all  depend  for  their  operation. 

Heat  is  developed  in  any  conductor  through  which  electricity  flows, 
and  the  temperature  of  the  conductor  is,  consequently,  raised.     The 


PRINCIPLES  OF  ELECTRICITY  AND  MAGNETISM 


heat  represents  the  loss  due  to  the  overcoming  of  the  resistance  by  the 
current.  The  amount  of  heat  developed  is  often  very  small  and  is  not 
noticeable.  Fuses  burn  out  because  of  the  heat  developed  in  them  by  the 
current.  When  the  current  becomes  excessive,  the  fuse  wire  melts  and 
opens  the  circuit,  protecting  it  from  possible  damage.  Incandescent 
lamps  produce  light  because  their  filaments  are  heated  white  hot  by  the 
passage  of  an  electric  current. 

The  chemical  action  due  to  an  electric  current  may  be  illustrated,  as 
in  Fig.  8,  by  submerging  the 
ends  of  two  wires,  connected  to 
battery  terminals,  in  a  glass  of 
water  in  which  a  little  salt  has 
been  dissolved.  The  current  in 
passing  through  the  water  will 
liberate  a  gas  (chiefly  hydrogen) 
in  the  form  of  fine  bubbles  which  BATTERY' 
will  rise  particularly  around  the 
negative  terminal.  This  simple 

test  is  very  valuable  to  remember  as  a  means  of  determining  the  posi- 
tive and  negative  of  two  direct-current  leads.  It  is  also  valuable  in 
distinguishing  between  alternating  and  direct  current,  since  alternating 
current  will  cause  bubbles  to  collect  equally  around  both  terminals. 

The  magnetic  effect  of  an  electric  current  can  be  readily  seen  when  a 
current  from  a  battery  passes  through  an  insulated  wire  wound  on  an 
iron  bar  as  shown  in  Fig.  9.  The  iron  bar  then  has  an  attraction  for 
other  pieces  of  iron,  and  is  said  to  be  magnetized. 

11.  Magnetism. — Certain 
metals  have  the  property  of 
being  able  to  attract  other 
metals.  This  property  is 


FIG.  8. — Chemical  effect  of  electric  current. 


IRON 


BATTERY^  ELECTRO -MAGNET 

FIG.  9. — Magnetic  effect  of  electric  current. 


CORE  known  as  magnetism,  and, 
while  it  is  not  known  pre- 
cisely just  what  magnetism 
is,  any  more  than  it  is  known 
what  electricity  is,  the  laws 
under  which  magnetism  acts  are  well  understood.  Although  electricity 
and  magnetism  are  closely  associated  they  are  entirely  different  and  one 
should  not  be  confused  with  the  other. 

12.  Natural  and  Artificial  Magnets. — Magnetism  obtained  its  name 
from  the  fact  that  certain  natural  iron  ores  found  near  Magnesia,  in  Asia, 
exhibited  this  attractive  power.  A  piece  of  ore  possessing  this  power 
was  called  a  magnet,  and  the  ore  itself  has  been  named  magnetite  or  lode- 
stone.  This  ore  is  the  only  known  form  of  natural  magnet.  The  mag- 
netic strength  of  this  material  is  not  sufficient  to  warrant*  its  being  used 


10  AUTOMOTIVE  IGNITION  SYSTEMS 

for  commercial  magnets.  It  is  possible  to  manufacture  magnets  having 
very  high  magnetic  strength,  and  these  will  be  the  only  magnets  which 
will  be  considered  in  this  volume. 

13.  Magnetic  and  Non-magnetic  Metals. — Only  certain  metals,  chiefly 
iron  and  steel  or  alloys  containing  these  metals,  and  nickel  to  a  lesser 
extent,  show  magnetic  properties.     These  metals  are  known  as  magnetic 
metals.     Metals  such  as  brass,  copper,  aluminum,  or  zinc,  which  do  not 
show  magnetic  properties,  are  called  non-magnetic  metals. 

Soft  iron  is  very  easily  magnetized,  but  it  loses  its  magnetic  proper- 
ties soon  after  the  magnetizing  influence  is  removed.  Magnets  made  of 
soft  iron  are  called  temporary  magnets.  A  bar  of  hardened  steel,  on  the 
other  hand,  after  being  magnetized  will,  with  proper  treatment,  retain 
its  magnetism  indefinitely.  Magnets  made  of  this  material  are  called 
permanent  magnets.  For  these  reasons,  magnets  which  must  become 
demagnetized  quickly,  such  as  the  cores  of  induction  coils,  are  made  of 
soft  iron — usually  in  the  form  of  a  bundle  of  soft  iron  wires — while  mag- 
nets which  must  retain  their  magnetic  strength,  such  as  the  magnets  on 
a  magneto,  are  made  of  hardened  nickel  steel,  chrome  steel,  or  tungsten 
steel. 

14.  The  Poles  of  a  Magnet. — Certain  parts  of  a  magnet  possess  the 
power  of  attracting  iron  to  a  much  greater  extent  than  other  parts. 
These  parts  are  called  poles.     In  a  bar  magnet  the  strength  is  greatest 
at  the  ends;  consequently,  the  ends  form  the  poles.     These  poles  differ 
from  each  other  in  certain  respects  and  are  called  the  North  and  the 
South  poles. 

The  force  which  draws  bits  of  iron  or  steel  to  the  magnet  is  said  to  be 
exerted  along  lines  which  extend  from  one  pole  of  the  magnet  through 
the  surrounding  space  to  the  other  pole.  These  lines  are  called  magnetic 
lines  of  force.  The  number  of  lines  of  force  present  in  any  particular 
part  of  the  space,  called  the  magnetic  field,  around  a  magnet  constitutes 
the  magnetic  flux  at  that  particular  point.  The  lines  of  force  are  invis- 
ible but  their  presence  may  be  easily  shown  by  placing  a  sheet  of  paper 
over  a  magnet  and  sprinkling  fine  iron  filings  upon  the  paper.  Upon 
gently  tapping  the  .paper,  the  filings  will  arrange  themselves  in  well- 
defined  lines  running  from  one  pole  to  the  other  as  shown  in  Fig.  10.  It 
will  be  noticed  that  each  line  runs  from  one  pole  to  the  other  in  the  short- 
est path  possible  without  touching  its  neighbor.  In  this  respect  they 
act  very  much  like  stretched  rubber  bands  tending  to  contract  as  much 
as  possible,  but  having  a  marked  aversion  to  touching  each  other. 

In  order  to  explain  many  of  the  phenomena  which  are  taken  up  later 
it  is  necessary  to  assign  direction  to  the  lines  of  force.  It  is  now  generally 
considered  that  the  lines  of  force  leave  the  magnet  at  the  North  pole,  go 
around  through  space  and  enter  the  magnet  at  the  South  pole,  continuing 
through  the  body  of  the  magnet  to  the  starting  point.  Each  line  of 


PRINCIPLES  OF  ELECTRICITY  AND  MAGNETISM       11 


force  makes  a  complete  loop.     An  interesting  point  in  the  study  of  the 

action  of  lines  of  force  lies  in  the  fact  that  they  never  touch  each  other 

and  never  cross  each  other,  however 

crowded  they  may  be.     The  direction 

of  the  lines  of  force  of  a  bar  and  a 

horseshoe  magnet  is  clearly  shown  in 

Fig.  11. 

When  two  magnets  are  brought 
together,  it  is  found  that  the  North 
pole  of  one  attracts  the  South  pole  of 
the  other,  and  that  two  like  poles, 
either  North  and  North  or  South  and 
South,  repel  each  other.  This  mag- 
netic attraction  or  repulsion  is  clearly 
shown  by  dipping  two  horseshoe  mag- 
nets in  iron  filings  and  noting  the 
formation  of  the  filings  when  the  poles  of  the  magnets  are  brought 
together  as  in  Fig.  12.  The  filings  will  form  in  metallic  strings  between 


FIG. 


10. — Field  of  a  bar  magnet  as  shown 
by  iron  filings. 


—   s 


FIG.  11. — Lines  of  force  around  bar  and  horseshoe  magnets. 


the  poles,  thus  showing  the  magnetic  attraction  between  unlike  poles. 
With  the  like  poles  brought  together,  as  in  Fig.  13,  the  filings  will  have 


FIG.  12. — Magnetic  attraction  of  unlike         FIG.  13. — Magnetic  repulsion  of  like  poles, 
poles. 

the  appearance  of  two  jets  of  water  being  forced  against  each  other, 
thus  showing  repulsion. 


12 


AUTOMOTIVE  IGNITION  SYSTEMS 


15.  The  Magnetic  Field. — The  zone  through  which  the  magnetic  flux 
or  lines  of  force  from  the  North  pole  pass  to  the  South  pole  is  known  as 
the  magnetic  field  of  the  magnet.  The  strength  of  this  field  depends  upon 
the  number  of  magnetic  lines  of  force  per  square  inch  at  that  part  of  the 
field  under  consideration. 

The  polarity  of  a  magnet  and  the  direction  of  its  magnetic  field  may  be 
readily  determined  by  using  a  compass  as  shown  in  Fig.  14.  The  North 


POCKET 
/COMPASS 


FIG.  14. — Use  of  a  compass  to  determine  magnetic  polarity. 

end  of  the  compass  needle  (the  end  which  naturally  points  toward  the 
geographical  North  pole)  will  ah  ays  point  in  the  direction  of  the  magnetic 
lines  of  force  or  toward  the  South  pole  of  the  magnet.  Likewise,  the 
south  end  of  the  compass  needle  will  point  toward  the  North  pole  of  the 
magnet. 


(A)  (B)      SIDE  VIEW  (C) 

LEFT  END  VIEW         (CURRENT  EUOWING  FROM          RIGHT  END  VIEW 
(CURRENT  GOING  INj  LEFT  TO  RIGHT)  CURRENT  GOING  OUT 

i          PIG.  15.- — Magnetic  lines  of  force  about  a  straight  conductor  carrying  current. 

16.  Electromagnetism. — Magnetism  which  is  produced  by  an  electric 
current  is  called  electromagnetism.  Experiments  show  that  a  wire  or 
any  other  form  of  conductor  which  carries  an  electric  current  will  have  a 
magnetic  field  set  up  around  it  in  a  right-handed  direction  to  the  current 
and  proportional  in  strength  to  the  amount  of  current  flowing.  This  fact 
constitutes  the  basis  for  the  important  relation  between  electricity  and 
magnetism.  The  magnetic  field  thus  produced  is  arranged  in  concentric 
circles  around  the  wire,  as  in  Fig.  15,  and,  like  the  field  of  a  magnet,  its 


PRINCIPLES  OF  ELECTRICITY  AND  MAGNETISM       13 


direction  can  be  determined  by  a  pocket  compass.     The  magnetic  needle, 
if  held  above  or  below  a  wire  carrying  a  direct  current,  will  turn  cross 


S 

FIG.  16. — Deflection  of  a  compass  needle  when  near  a  conductor  carrying  a  current. 

wise  of  the  wire,  as  in  Fig.  16,  with  the  North  end  of  the  compass  pointing 
around  the  wire  in  the  direction  of  the  magnetic  lines  of  force.  By  thus 
determining  the  direction  of  magnetic 
field  around  the  wire,  the  direction  of 
current  flowing  in  the  wire  may  also 
be  determined. 

If  the  wire  is  coiled  into  a  loop,  as 
in  Fig.  17,  it  will  be  found  that  the 
lines  of  force  all  enter  the  same  face  of 
the  loop  and  come  out  of  the  other 
face.  If  two  loops  are  placed  close 
together,  as  in  Fig.  18  A,  the  lines  of 
force  will  join  and  go  around  the  two 
wires  together  instead  of  around  each 
one  alone.  The  same  is  also  true  of 
the  lines  of  force  surrounding  two 


FIG. 


17. — Magnetic   field   produced   by 
current  in  a  single  loop. 


parallel  wires  placed  close  together  in  which  both  wires  are  carrying 
current  in  the  same  direction  as  in  Fig.  18  B.     If  a  number  of  turns  of 


FIG.  18. — Magnetic  lines  of  force  around  two  adjoining  loops  carrying  current  in  the  same 

direction. 

insulated  wire  are  wound  into  a  coil,  as  in  Fig.  19,  nearly  all  the  lines  of 
force  will  enter  one  end  of  the  coil,  pass  through  it,  leave  the  opposite  end, 


14 


AUTOMOTIVE  IGNITION  SYSTEMS 


and  return  outside  of  the  coil  to  the  starting  point.  A  helical  coil  carry- 
ing an  electric  current  has  the  same  character  of  magnetic  field  as  a  bar 
magnet  having  a  North  pole  where  the  lines  of  force  leave  the  coil  and 
a  South  pole  where  the  lines  of  force  enter  the  coil.  Such  a  coil  carrying 
an  electric  current  is  called  a  solenoid. 

17.  The  Electromagnet. — The  magnetic  strength  of  a  solenoid  is  not 
great,  but  may  be  made  so  by  inserting  a  core  of  soft  iron  or  steel,  as 
in  Fig.  20,  converting  it  into  an  electromagnet.  The  iron  has  the  property 


FIG.   19. — Lines  of  force  through  a  coil  or  solenoid. 

of  conducting  magnetic  lines  of  force  much  more  readily  than  the  air; 
hence,  a  solenoid  with  an  iron  core  will  have  greater  magnetic  strength 
than  a  simple  solenoid  without  a  core. 

The  strength  of  the  electromagnet  may  also  be  increased  by  increasing 
either  the  amount  of  current  flowing  through  the  winding,  or  the  number 
of  turns  in  the  coil,  or  both.  In  fact,  the  magnetic  pull  of  the  core  will 
depend  not  only  on  the  size  and  length  of  the  core,  but  on  the  number  of 

_  ^ amperes     multiplied     by     the 

number  of  turns  in  the  wind- 
ing, or  the  total  number  of 
ampere-turns  producing  the 
magnetism.  If  the  coil  in  Fig. 
20  consists  of  10  turns  of  wire 
through  which  a  current  of  8 


FIG.  20. — Lines  of  force  through  an  electromagnet. 


amperes  is  flowing,  the  mag- 
netic strength  of  the  core  will 
be  due  to  10  X  8  or  80  ampere-turns. 

18.  To  Determine  the  Polarity  of  an  Electromagnet.— A  simple  method 
for  determining  the  polarity  of  an  electromagnet,  if  the  direction  of  cur- 
rent is  known,  is  to  grasp  the  coil  in  the  right  hand  with  the  fingers  point- 
ing around  the  core  in  the  same  direction  as  the  current  flowing  in  the 
winding.  With  the  hand  in  this  position,  the  thumb  will  naturally 
point  in  the  direction  of  the  magnetic  lines  of  force  or  along  the  core  to 
the  North  pole. 

The  polarity  of  an  electromagnet  may  also  be  quickly  determined  by 


PRINCIPLES  OF  ELECTRICITY  AND  MAGNETISM       15 


holding  a  compass  near  its  poles.  The  North  end  of  the  needle  will 
point  to  the  South  pole  of  the  magnet  as  already  illustrated  in  Fig.  14. 

19.  Electromagnetic  Induction. — It  was  pointed  out  in  the.  preceding 
paragraphs  that  a  current  flowing  in  a  conductor  creates  a  magnetic 
field  around  the  conductor  in  a  right-handed  direction  to  the  flow  of  current 
as  shown  in  Fig.  15.  It  will  also  be  found  that  if  a  magnetic  field  is  set 
up  around  a  conductor  an  electric  current  will  be  caused  to  flow  in  the  con- 
ductor, and  that  the  same  relation  will  exist  between  the  direction  of 
current  flow  and  the  magnetic  field.  This  relation  is  shown  very  clearly 
in  Fig.  21  in  which  the  forward  travel  of  the  screw  represents  the  direction 
of  current,  and  the  rotation  of  the  screwdriver,  the  direction  of  magnetism. 

The  process  of  generating  a  current  in  this  manner  is  known  as  electro- 
magnetic induction}  and  the-  current  thus  produced  is  called  an  induced 
current.  If  the  current  is  generated  by  magnetism  alternating  in  direc- 
tion, the  induced  current  will  also  be  alternating  in  direction,  with  as 
many  reversals  through  the  wire  per  second  as  there  are  reversals  of 


DIRECTION  OF  CURRENT 


DIRECTION  Of 
MAGNETIC  FIELD 


FIG.   21. — Relation  between  direction  of  current  and  magnetic  field. 

magnetism.     Such  a  current  is  called  alternating  current  and  is  usually 
abbreviated  A.  C. 

A  magnetic  field  may  be  set  up  around  a  wire  in  two  ways:  either  by 
cutting  a  magnetic  field  with  a  wire,  such  as  rotating  an  armature  of  a 
magneto  or  generator  in  a  magnetic  field;  or  by  cutting  the  wire  or  coil  of 
wire  with  a  rapidly  moving  magnetic  field  as  found  in  the  inductor  type 
magneto  and  in  the  induction  coil. 

"he  method  by  which  a  magnetic  field  is  set  up  around  a  conductor 
and  the  relative  direction  of  the  induced  current  are  illustrated  by  Fig. 
22  A,  B,  and  C  in  which  N  and  S  represent  the  North  and  South  poles  of  a 
magnet  and  W  a  wire  cutting  through  the  magnetic  field  between  N  and 
S  in  a  downward  direction.  The  magnetic  lines  of  force  between  N  and 
S  cause  an  attraction  between  the  two  poles,  like  that  of  many  rubber 
bands  under  tension.  It  is  evident  that  the  rubber  bands,  if  intercepted 
by  a  moving  wire,  will  be  crowded  ahead  as  indicated  in  Fig.  22  B.  In 
a  similar  way,  it  may  be  supposed  that  the  magnetic  lines  of  force  will 
be  distorted  by  the  moving  wire  as  shown  in  Fig.  22  C.  From  this  figure 
it  will  be  noted  that  the  distorted  lines  of  force  crowding  ahead  of  the 
moving  conductor  or  wire  will  create  a  field  of  greater  intensity  on  one 


16 


AUTOMOTIVE  IGNITION  SYSTEMS 


side  of  the  conductor  than  on  the  other.  This  will  have  the  effect  of 
setting  up  a  magnetic  whirl  around  the  conductor  in  an  anti-clockwise 
direction,  thereby  inducing  voltage  and  current  in  the  conductor  as  indi- 
cated by  the  arrows.  This  whirl  of  magnetic  lines  may  be  likened  in 
direction  to  a  whirlpool  caused  by  water  turning  a  sharp  bend  in  a  creek, 
as  in  Fig.  23,  in  which  the  water  corresponds  to  the  magnetic  lines  of  force. 


FIG.  22. — Principle  of  electromagnetic  induction. 

In  this  example  the  field  was  considered  stationary  and  the  wire 
movable.  If  instead  the  wire  should  be  stationary  and  the  magnetic 
lines  made  to  cut  the  wire,  as  in  Fig.  24,  the  effect  would  also  be  the  same, 
resulting  in  a  current  and  voltage  being  induced  in  the  wire.  In  either 
case,  the  current  will  be  set  up  in  the  wire  in  a  direction  which  will 


WHIRLPOOL 


FIG.  23.  —  Water  analogy  of  magnetic  whirl 
around  a  conductor. 


FIG.  24.  —  Magnetic  lines  of  force 
cutting  a  conductor. 


depend  upon  the  direction  of  the  magnetic  lines  between  the  poles  and 
upon  the  direction  in  which  the  wire  cuts  the  magnetic  lines  of  force. 
The  current  thus  produced  is  proportional  in  strength  to  the  resistance 
of  the  wire,  to  the  strength  of  the  magnetic  field,  and  to  the  speed  at  which 
the  magnetic  lines  of  force  are  cut. 


PRINCIPLES  OF  ELECTRICITY  AND  MAGNETISM       17 

The  Right-hand  Rule. — An  easy  way  to  determine  the  relation  between 
the  induced  current,  the  direction  of  magnetism,  and  the  motion  of  the 
wire  through  the  magnetic  field  is  by  holding  the  thumb  and  first  two 
fingers  of  the  right  hand  at  right  angles  as  shown  in  Fig.  25.  If  the  thumb 

DIRECTION  OF 


INDUCED.CURRENT 


MOTION    OF 
CONDUCTION 


:CTION  OF 

MAGNETISM 


FIG.  25. — Right-hand    three-finger   rule   for   determining   direction   of   induced    current. 

is  made  to  point  in  the  direction  of  the  magnetic  field,  and  the  second 
finger  in  a  direction  corresponding  to  the  relative  motion  of  the  con- 
ductor, the  first  finger  will  naturally  point  along  the  conductor  in  the 
direction  of  the  induced  current. 


CHAPTER  II 


^-Carbon 


IGNITION  BATTERIES 

20.  Primary  and  Secondary  Batteries. — The  most  essential  part  of 
any  electrical  ignition  system  is  the  source  of  electric  current.  For  this 
purpose  a  battery,  generator,  or  magneto  may  be  used.  In  the  battery 
ignition  system  the  current  is  supplied  by  either  a  dry  battery  made  up 
of  a  number  of  dry  cells,  or  by  a  storage  battery  composed  of  a  number  of 
storage  cells.  The  number  of  cells  used  with  either  type  of  battery  de- 
pends upon  the  voltage  and  current 
required  to  operate  the  system. 

A  cell,  in  its  simplest  form,  con- 
sists of  two  plates,  which  may  be  of 
two  different  metals,  or  one  plate  may 
be  of  metal  and  the  other  of  carbon, 
immersed  in  such  a  manner  that  the 
plates  do  not  touch  each  other  in  a 
vessel  containing  a  chemical  solution 
called  electrolyte.  The  chemical  solu- 
tion acts  upon  the  plates  in  such  a 
way  that  a  difference  in  potential  or 
voltage  is  created  between  the  two 
plates.  When  the  two  plates  are 
joined  by  a  conductor,  this  pressure 
or  voltage  causes  a  current  to  flow 
through  the  conductor.  Cells  may  be 
grouped  under  two  classes;  namely, 
primary  and  secondary,  according  to  their  construction  and  principle  of 
operation. 

The  primary  cell  may  be  further  classified  as  wet  or  dry,  according  to 
the  nature  of  its  electrolyte.  In  the  wet  cell,  the  electrolyte  is  in  the  form 
of  a  liquid,  while  in  the  dry  cell  it  is  in  the  form  of  a  wet  paste  which  will 
not  flow  or  splash.  An  example  of  the  wet  cell  is  shown  in  Fig.  26  in 
which  the  two  plates,  called  elements,  of  carbon  and  zinc  are  immersed 
in  a  solution  of  salammoniac  in  water.  When  the  terminals  of  the  cell 
are  connected  so  as  to  form  a  circuit,  chemical  action  will  take  place 
between  the  electrolyte  and  the  elements,  resulting  in  a  flow  of  electricity 
through  the  electrolyte  from  the  zinc  to  the  carbon  elements,  and 
through  the  external  circuit  from  the  carbon  terminal  to  the  zinc  terminal 

19 


FIG.  26. — Wet  primary  cell. 


20  AUTOMOTIVE  IGNITION  SYSTEMS 

and  element.  Such  a  cell,  owing  to  its  low  voltage  (usually  about  1  volt) 
and  the  relatively  small  current  output  in  proportion  to  its  size  and 
weight,  is  very  inconvenient  to  use  for  automobile  ignition.  For  this 
service,  the  dry  cell,  Fig.  27,  has  gained  much  favor,  since  it  gives  a  much 
higher  voltage  and  current  output,  namely,  1^  volts  and  25  to  30 
amperes  when  new,  and  is  much  more  convenient  to  handle.  The  chief 
characteristic  of  any  primary  battery  is  the  fact  that  as  electrical  energy 
is  produced,  one  of  the  elements  is  destroyed  by  the  chemical  action. 
When  a  primary  cell  has  become  exhausted,  it  can  be  replenished  only 
by  renewing  either  the  elements  or  the  electrolyte,  or  both.  In  the  case 
of  dry  cells  it  is  more  convenient  and  cheaper  to  replace  the  entire  cell 
with  a  new  one. 

The  secondary  battery,  commonly  known  as  the  storage  battery,  Fig. 
40,  which  is  now  universally  employed  by  automobile  manufacturers 
for  electric  starting,  lighting,  and  ignition  purposes,  differs  from  the 
primary  battery  in  that  it  may  be  charged  and  discharged  many  times 
without  renewing  either  the  elements  or  the  electrolyte.  A  secondary 
cell  must  first  be  charged  by  sending  a  direct  current  through  it,  thereby 
causing  the  elements  to  undergo  an  electro-chemical  change;  then,  when 
the  cell  is  used  as  a  source  of  current,  the  current  discharge  is  accom- 
panied by  a  reverse  chemical  change  which  changes  the  elements  or  plates 
back  to  their  original  composition.  Consequently,  a  cell  of  this  type  can 
be  used  repeatedly  by  providing  a  means  of  recharging  when  it  becomes 
exhausted  or  discharged., 

21.  The  Dry  Cell. — The  dry  cell,  Fig.  27,  has  been  used  very  exten- 
sively in  the  past  for  passenger  automobile  ignition  purposes  and  is  still 
used  extensively  for  tractor,  truck,  and  stationary  engine  ignition,  al- 
though it  is  being  rapidly  supplanted  by  the  storage  battery  and  magneto 
as  a  source  of  current.  It  consists  of  a  cylindrical  zinc  shell  or  can,  the 
inside  of  which  is  usually  lined  with  absorbent  paper  saturated  with  a 
solution  of  salammoniac  and  zinc  chloride.  The  zinc  shell  forms  the 
negative  terminal  of  the  battery,  and  the  carbon  element  placed  in 
the  center  of  the  cell  forms  the  positive  terminal.  The  space  between 
the  absorbent  paper  and  the  carbon  is  filled  with  a  mixture  of  crushed 
coke,  graphite,  and  manganese  dioxide.  This  mixture  is  also  saturated 
with  salammoniac  and  zinc  chloride.  The  purpose  of  the  crushed  carbon 
and  manganese  dioxide  mixture  is  to  act  as  a  depolarizing  agent. 

Polarization. — When  a  dry  cell  discharges  rapidly,  the  flow  of  current 
through  the  electrolyte  (the  electrolyte  is  the  salammoniac  and  zinc  chlor- 
ide which  saturates  the  carbon  mixture),  causes  hydrogen  gas  to  be  liber- 
ated. The  gas  accumulates  in  the  form  of  bubbles  around  the  carbon 
or  positive  element  of  the  cell.  This  action  is  known  as  polarization. 
The  gas  thus  formed  tends  to  insulate  the  carbon  rod  from  the  electro- 
lyte, thereby  increasing  the  internal  resistance  and  decreasing  the  current 


IGNITION  BATTERIES 


21 


output.  The  manganese  dioxide,  which  is  rich  in  oxygen,  acts  to  depol- 
arize or  absorb  this  gas  by  the  combining  of  the  oxygen  and  hydrogen, 
forming  water.  If  the  cell  discharges  slowly,  the  hydrogen  is  united  with 
the  oxygen  as  rapidly  as  released.  However,  when  the  discharge  rate  is 
high,  the  hydrogen  is  released  too  rapidly  to  be  taken  up  by  the  oxygen 
in  which  case  the  cell  will  polarize.  If  the  cell  is  allowed  to  stand  for  a 
short  time,  to  permit  the  hydrogen  to  be  absorbed,  it  will  regain  its 
normal  condition. 

Nearly  all  American  dry  cells  used  for  ignition  are  2j^  in.  in  diameter 
and  6  in.  high,  which  size  is  usually  referred  to  as  No.  6.  The  top  is 
sealed  with  a  special  compound  to  make  it  air-  and  water-tight.  The 
entire  cell,  except  the  top,  is  wrapped  with  pasteboard  to  prevent  the 
zinc  making  contact  with  other  zinc  cans  in  the.  set.  The  voltage  of  a 


ZINC  oft 
-TERMINAL 


FINE  SANO 


ABSORBENT  " 
PAPER 


MOISTENED  WITH 
5/U AMMONIAC  AW 
ZINC  CHLORIDE 
SOLUTION 


FIG.  27.— The  dry  cell. 


good  dry  cell  on  open  circuit  is  about  1J^  volts.  The  maximum  current 
or  amperage  which  it  will  give,  when  new,  ranges  from  20  to  35  amperes, 
depending  upon  the  size  of  the  cell  and  the  temperature.  A  No.  6  cell 
giving  more  than  25  to  30  amperes  will  probably  polarize  rapidly.  Cell 
capacity  and  life  depend  largely  on  the  way  the  cell  is  used,  both  being 
greater  when  it  is  used  intermittently. 

The  Dry  Cell  Always  Gives  out  Direct  Current. — Not  all  dry  cells  are 
suitable  for  ignition.  Cells  which  may  be  suitable  for  intermittent  use  on 
doorbells,  annunciators,  telephones,  etc.  may  have  a  rather  high  internal 
resistance.  By  resistance  is  meant  the  opposition  offered  to  a  flow  of 
current.  Ignition  cells  should  be  constructed  so  as  to  have  a  low  internal 
resistance.  In  addition  to  this,  a  special  effort  should  be  made  to  reduce 
polarization  to  a  minimum. 


22 


AUTOMOTIVE  IGNITION  SYSTEMS 


22.  Testing  Dry  Cells. — The  voltage  of  a  cell  depends  upon  the  kind 
and  quality  of  the  elements,  the  composition  of  the  electrolyte,  and  the 
temperature.  With  identical  materials,  a  small  cell  will  show  the  same 
voltage  as  a  large  one.  On  the  other  hand,  the  amperage  or  capacity  of 
a  cell  depends  upon  its  size.  If  the  terminals  of  a  voltmeter  are  connected 
across  the  terminals  of  a  new  dry  cell,  a  reading  of  about  1.5  volts  will 
be  recorded.  The  voltage  of  an  exhausted  cell  is  almost  as  high  as  a 
new  one;  consequently,  the  voltage  test  of  a  dry  cell  does  not  furnish 
accurate  information  as  to  its  condtion. 

The  standard  method  of  testing  dry  cells  is  by  the  use  of  an  ammeter. 
This  is  an  instrument  that  indicates  the  rate  of  flow  of  current  in  amperes. 

Figure  28  shows  a  combination  volt- 
meter and  ammeter,  known  as  a  volt- 
ammeter,  such  as  is  usually  used  for 
dry  eel!  testing.  The  flexible  ter- 
minal is  in  both  the  ammeter  and  volt- 
meter circuits.  When  used  to  test  dry 
cells,  the  flexible  terminal  and  the 
terminal  marked  Amp.  are  touched  to 
the  dry  ecll  terminals,  the  stationary 
terminal  being  connected  to  the  center 
terminal  or  positive  and  the  flexible 
terminal  to  the  zinc  or  negative.  The 
needle  will  move  across  the  scale  and 
indicate  the  current  strength  of  the 
cell.  When  new,  the  reading  for  a 
No.  6  ignition  cell  should  be  between 
25  and  30  amperes.  A  reading  below 
8  amperes  shows  that  the  cell  is  nearly 
exhausted  and  cannot  be  considered 
as  a  reliable  source  of  energy. 

There  is  a  perceptible  difference  in 
the  action  of  cells  at  various  temperatures.  It  is  difficult  for  the  chemical 
action  to  take  place  fast  enough  at  a  temperature 'of  zero  or  below;  con- 
sequently, the  cell  will  test  lower  than  at  normal  temperatures.  On  the 
other  hand,  heat  stimulates  the  chemical  action  causing  the  cell  to  test 
higher  than  at  normal  temperatures.  Heat  will  also  cause  a  rapid  de- 
terioration of  dry  cells.  When  not  in  use,  they  should  be  stored  in  a 
cool  dry  place  to  prevent  this  rapid  deterioration. 

A  rough  test  to  determine  if  a  cell  is  good  can  be  made  by  short  cir- 
cuiting the  terminals  momentarily  by  means  of  a  wire.  If  a  small  arc 
can  be  drawn  between  the  wire  and  the  carbon  post,  the  cell  is  at  least 
in  fair  condition.  The  test  can  also  be  made  by  stretching  a  piece  of 
fine  copper  wire  of  about  No.  28  or  30  gage  across  the  terminals.  If  it 


FIQ.  28. — Typical  pocket  volt-ammeter 
for  testing  dry  cells. 


IGNITION  BATTERIES 


23 


fuses  instantly,  it  proves  that  the  cell  will  test  between  15  and  20  amp. 
if  tested  with  an  ammeter.  Another  method  is  to  rest  a  knife  blade  on 
the  zinc  post  and  to  touch  the  tip  of  the  blade  to  the  carbon.  If  a  small 
ring  of  smoke  appears  at  the  point,  the  cell  is  in  fair  condition. 

23.  Wiring  of  Ignition  Batteries. — When  the  current  for  ignition  is 
supplied  by  a  storage  battery,  the  voltage  is  usually  either  6  or  12  volts. 
This  voltage  is  fixed  by  the  design  of  the  starting  and  lighting  system 
which  generally  uses  the  same  voltage  as  the  ignition  system  and  which 
operates  from  the  same  battery.  The  battery  may  vary  in  size  from  60 


6  VOLTS 


FIG.  29. — Cell  connections  for  a  six-volt     FIG.  30. — Cell  connection's  for  a  twelve-volt 
storage  battery.  storage  battery. 

to  130  ampere-hour  capacity,  depending  upon  the  requirements  of  the 
starting  and  lighting  system.     Each  storage  cell  gives  approximately 

2  volts;  consequently,  the  proper  voltage  may  be  obtained  by  connecting 

3  cells  in  series;  that  is,  connecting  the  Positive  (+)  terminal  of  one  cell 
to  the  Negative  (  — )  terminal  of  the  next  as  shown  in  Fig.  29.     In  like 
manner,  a  12- volt  storage  battery  must  have  6  cells  connected  in  series 
as  in  Fig.  30. 

When  dry  cells  are  used  for  ignition,  two  methods  of  connecting  several 
cells  may  be  resorted  to  in  order  to  raise  the  voltage  and  amperage  to 


5  Dry  cells  in  series 
FIG.  31. 


6  Dry  ce/Is  in  para//e/ 
FIG.  32. 


the  proper  amount,  namely,  through  series  or  parallel  connection.  The 
series  method  of  connection  is  shown  in  Fig.  31  in  which  the  carbon  or 
Positive  of  one  cell  is  connected  to  the  zinc  or  Negative  of  the  next,  leaving 
one  carbon  and  one  zinc  free  for  connection.  Thus  the  current  has  to 
pass  through  the  entire  set  of  cells  to  complete  its  circuit.  This  method 
increases  the  voltage  as  many  times  as  there  are  cells.  The  five  cells  of 
Fig.  31,  each  giving  about  1^  volts  will,  when-  connected  in  series, 


24 


AUTOMOTIVE  IGNITION  SYSTEMS 


furnish  a  current  at  5  X  IJ^,  or  7J^  volts  pressure.  The  current  output 
is  equal  to  the  current  of  one  cell,  or  about  20  amperes.  If  all  the  car- 
bons are  connected  and  all  the  zincs  fastened  together,  as  shown  in  Fig. 
32,  the  connection  is  known  as  parallel.  The  resultant  voltage  equals 
the  voltage  of  one  cell,  and  the  current  output  equals  the  current  output 
of  one  cell  multiplied  by  the  total  number  of  cells.  For  example,  the 
current  output  of  5  cells  connected  in  parallel  would  be  5  X  20  or  100 

amperes  and  the  voltage  would  be  1^£ 
volts.  Therefore,  to  increase  the  voltage, 
the  cells  are  connected  in  series,  and  to  in- 
crease the  current  output  they  are  con- 
nected in  parallel. 

Where  the  current  demand  is  small  or  not 
continuous,  5  cells  connected  in  series  may 
be  used.  This  arrangement  gives  7%  volts 

and  20  amperes  and  is  suitable  for  single  cylinder  engines  or  for  starting 
engines  of  two  or  more  cylinders  where  a  magneto  is  used  after  the  engine 
is  in  operation.  It  is  also  suitable  for  battery  ignition  systems  designed 
so  as  to  be  very  economical  in  the  use  of  current. 

When  the  amount  of  current  required  is  great  and  a  storage  battery 
is  not  available,  the  multiple  series  connection  may  be  used.  This  is 
suitable  for  engines  of  two  or  more  cylinders  and  for  continuous  service. 


FIG.  34. — Ignition  circuit  with  two  sets  of  dry  cells  for  alternate  use. 

The  arrangement  consists  of  parallel  groups  of  as  many  cells  in  series 
as  may  be  required  for  the  service.  Figure  33  shows  an  arrangement  with 
three  parallel  sets,  each  having  5  cells  connected  in  series.  This  arrange- 
ment provides  for  a  current  of  about  60  amperes  at  7^  volts. 

A  scheme  for  using  two  distinct  sets  of  cells  is  often  employed  as 
shown  in  Fig.  34.  By  means  of  the  three-point  switch,  the  two  sets  of 
cells  can  be  used  alternately.  This  scheme  allows  relatively  long  periods 
for  recuperation  of  the  cells. 


IGNITION  BATTERIES  25 

24.  Care  of  Dry  Cells. — Dry  cells  are  subject  to  a  trouble  known  as 
local  action.  Unless  the  zinc  of  which  the  container  is  made  is  very  pure, 
chemical  action  will  be  set  up  between  the  zinc  and  any  impurity,  such 
as  particles  of  iron.  This  chemical  activity  is  known  as  local  action  and 
will  cause  the  zinc  to  be  rapidly  destroyed.  The  moisture  rapidly  finds 
its  way  out  of  the  openings,  and  as  a  result  the  cell  dries  out  and  be- 
comes worthless. 

If  the  cells  are  located  in  a  damp  place,  trere  is  a  possibility  of  the 
paper  covers  absorbing  enough  moisture  to  set  up  a  local  circuit  between 
the  cells.  This  means  that  the  cells  will  be  continuously  discharging. 
In  order  to  avoid  deterioration  of  the  cells  from  this  cause,  it  is  advisable 
to  avoid  wet  locations  for  the  cells.  Cells  which  must  be  used  in  such 
locations,  however,  can  be  protected  to  a  great  extent  by  being  imbedded 
in  paraffin.  With  this  arrangement,  local  discharge  cannot  take  place, 
neither  can  moisture  escape  through  any  holes  in  the  zinc  which  may 
result  from  local  action. 

25.  Storage  Cells. — In  storage  cells,  the  current  results  from  chemical 
action,  as  in  any  primary  cell.  When  the  cells  are  exhausted,  however, 
they  need  not  be  discarded  or  the  elements  replaced,  but  instead  may  be 
restored  to  normal  condition  by  passing  a  direct  current  through  them. 
By  this  process,  a  reverse  chemical  change  takes  place,  restoring  the 
elements  to  their  original  structure.  It  is  erroneous  to  say  that  electric- 
ity is  stored  in  the  elements  of  a  storage  cell.  In  reality,  the  storage 
cell  is  a  device  which  converts  -  electrical  energy  into  chemical  energy 
during  charge,  and  reconverts  the  chemical  energy  back  into  electrical 
energy  during  discharge.  The  energy  stored  is  in  the  form  of  chemical 
energy.  When  the  current  is  drawn  from  the  cell,  the  chemical  action 
takes  place,  thus  converting  chemical  energy  into  electrical  energy. 

There  are  two  kinds  of  storage  cells  in  use,  the  nickel-iron  type  and  the 
lead  type.  The  former  consists  of  elements  of  nickel  and  iron  compounds 
in  a  solution  of  caustic  potash.  The  latter  consists  of  two  groups  of  lead 
composition  plates  immersed  in  a  solution  of  sulphuric  acid.  Both  types 
of  cells  may  be  put  up  in  either  stationary  or  portable  form,  the  latter 
always  being  used  for  automobile  purposes. 

26.  The  Edison  Storage  Battery. — A  typical  Edison  storage  battery 
suitable  for  ignition  and  lighting  purposes  is  shown  in  Fig.  35.  This 
battery  was  developed  by  Thomas  A.  Edison  in  an  attempt  to  overcome 
the  objectionable  features  of  the  lead  storage  battery,  such  as  heavy 
weight,  acid  fumes,  and  rapid  deterioration.  The  plates  are  composed  of 
iron  and  nickel,  the  container  is  nickel-plated  steel,  and  the  electrolyte 
is  a  solution  of  caustic  potash.  The  top  of  the  cell,  showing  the  filling 
aperture  for  adding  water,  is  shown  in  Fig.  36. 

The  complete  element  of  the  Edison  cell  is  shown  in  Fig.  37.  The 
negative  plate,  Fig.  38A,  consists  of  a  steel  grid  containing  pockets  filled 


26 


AUTOMOTIVE  IGNITION  SYSTEMS 


with  iron  oxide,  such  a  pocket  being  shown  in  Fig.  38B.  The  positive 
element,  Fig.  39 A,  consists  of  thirty  perforated  steel  tubes  reinforced 
by  steel  seamless  rings  equi-distantly  spaced  and  mounted  on  a  steel  grid. 
Each  perforated  tube,  Fig.  39#,  is  filled  with  alternate  layers  of  nickel 


FIG.  35. — Edison  storage  battery. 


FIG.  36. — Top  of  Edison  storage  cell  showing 
filling  aperture  open  for  adding  water. 


FIG.  37. — Edison  cell  assembled,     FIG.  38. — (A)  Edison  negative  plate.     (B)  Pocket 
but  removed  from  container.  for  negative  plate.     (Iron  oxide). 

hydrate  and  flake- nickel.  During  charge  and  discharge,  the  solution  of 
caustic  potash  transfers  oxygen  from  one  element  to  the  other.  The 
positive  and  negative  plates  are  insulated  by  several  hard  rubber  rods 
between  them.  The  voltage  of  each  cell  is  normally  about  1.1  volts,  the 
capacity  depending  upon  the  size  and  number  of  plates  in  the  cell. 


IGNITION  BATTERIES 


27 


Although  the  Edison  nickel-iron  type  of  battery  has  the  advantages 
of  great  mechanical  strength,  long  life,  and  a  relatively  high  capacity 
(at  a  low  discharge  rate)  per  pound  of  cell,  it  is  not  so  well  adapted  for 
automobile  service  as  is  the  lead  type  of  battery.  This  is  due  to  the 
lower  normal  voltage  of  the  Edison  cell  (being  about  1.1  volts  per  cell  or 
approximately  one-half  as  high  as  that  of  the  lead  cell),  its  rapid  drop  in 
voltage  and  efficiency  in  cold  weather,  and  its  inability  to  discharge  at  a 
high  rate  for  the  short  time  necessary  to  operate  the  starting  motor. 

Since  a  battery  capable  of  giving  a  high  current  output  for  a  short 
period  is  required  to  operate  the  starting  motor, 
and  since  it  must  also  operate  under  a  very  wide 
range  of  temperature  conditions,  the  Edison  battery 
is  seldom  used  on  the  automobile,  other  than  for 
lighting  and  ignition  purposes.  The  lead  storage 


'    Fio.  39- — (A)  Positive  plate  (nickel  hydrate) .      (B)  Tube  for  positive  plate. 

•battery  has  been  satisfactorily  developed  to  meet  all  these  requirements; 
consequently,  it  has  been  universally  adopted  by  automobile  manufac- 
turers as  standard  equipment  for  starting,  lighting,  and  ignition  purposes. 
27.  The  Lead  Storage  Battery. — A  typical  storage  battery  as  used  for 
automobile  starting,  lighting,  and  ignition  purposes  is  shown  in  Fig.  40. 
The  battery  may  consist  of  three  or  more  cells,  depending  upon  the  volt- 
age desired.  Each  cell  has  an  electrical  pressure  of  about  2  volts;  conse- 
quently, a  battery  of  3  cells  connected  in  series  is  known  as  a  6-volt 
battery  and  one  of  6  cells  connected  in  series  is  known  as  a  12-volt 
battery. 


28 


AUTOMOTIVE  IGNITION  SYSTEMS 


Each  cell  consists  of  a  hard  rubber  jar  in  which  is  placed  two  kinds  of 
lead  plates  known  as  positive  and  negative.     These  plates  are  separated  or 

held  apart  from  each  other  by  suitable 
separators  and  are  submerged  in  a  solu- 
tion of  sulphuric  acid  and  water.  A 
sectional  view  of  a  typical  lead  storage 
cell  showing  the  construction  and 
arrangement  of  parts  is  shown  in  Fig. 
41.  As  the  lead  plate  storage  battery 
produces  current  at  a  pressure  of  but  2 
volts  per  cell,  a  single  cell  is  rarely  used. 
The  lowest  number  of  cells  in  practical 
use  is  found  in  the  three-cell  6-volt 
-P  An  ™  battery,  the  different  cells  being  per- 

FIG.  40. — Typical  6-volt  automobile 

storage  battery.  manently  connected  together  by  heavy 

lead  strips,  while  detachable  terminals 
are  provided  for  connecting  the  battery  to  an  outside  circuit. 


Handle 


Verrt-  Plugs, 


Negative  Battery         /    * 
..•.•*"•  .  ^v-*        ii,  */  •ll'tii 


P<?5it/ve 
Battery 
Terminal 


Jar  Cover 


Expansion 
Chamber  for 
Electrolyte 


'Separators 


Hard 
Rubber 

Jar 


Hardwood  &<?. 


5edfrnent  Space 


FIG.  41. — Section  of  typical  lead  storage  battery. 

Plates. — Each  plate  consists  of  a  grid  or  framework,  Fig.  42,  composed 
of  lead  and  antimony,  the  openings  of  which  are  pasted  full  of  a  lead 
compound  known  as  active  material.  Wl  en  dry,  this  active  material 


IGNITION  BATTERIES 


29 


becomes  hard  like  cement.  The  plates  are  then  put  tr  rough  an  electro- 
chemical process  which  converts  the  active  material  of  the  positive 
plates  into  brown  peroxide  of  lead,  Fig.  43,  and  that  of  the  negative 
plates  into  a  gray  spongy  metallic  lead  as  shown  in  Fig.  44.  This  proc- 
ess is  known  as  forming  the  plates. 


FIG.  42. — Types  of  grids  for  battery 
plates. 


FIG.  43. — Positive 
plate. 


FIG.  44. — Negative 
plate. 


After  the  positive  and  negative  plates  have  been  formed,  they  are 
built  into  positive  and  negative  groups  as  in  Fig.  45.  A  positive  group 
consists  of  one  or  more  positive  plates  burned  to  a  connecting  strap  and  a 
negative  group  of  two  or  more  negative  plates  connected  to  a  similar 


FIG.  45. — Battery  group. 


FIG.  46. — Battery  element. 


connecting  strap.  To  each  strap  is  attached  a  post  which  is  used  to  make 
electrical  connection  between  two  adjoining  groups  or  to  the  starting  and 
lighting  system.  One  positive  and  one  negative  group,  together  with  the 
separators,  form  an  element  as  shown  in  Fig.  46.  The  negative  group 
always  has  one  more  plate  than  the  positive  group  as  shown  in  Fig.  47, 


so: 


AUTOMOTIVE  IGNITION  SYSTEMS 


This  is  true  regardless  of  the  number  of  plates  in  the  element.  For  ex- 
ample, a  three-plate  'element  would  have  one  positive  and  two  negative 
plates,  and  a  five-plate  element  would  have  two  positive  and  three  nega- 
tive plates.  .  rti  tr 

The  plates  are  welded  or  "burned"  to  the  connecting  straps  usually  by  a 
hydrogen  or  oxy-acetylene  flame  so  that  the  plates  and  strap  form  one  unit. 


I 


FIG.  47. — Positive  and  negative  group. 


FIG.  48. — Rubber  jars. 


The  plates  are  so  arranged  that  when  the  element  is  assembled,  each 
positive  plate  surface  is  adjacent  to  a  negative  plate  surface,  the  distance 
between  these  surfaces  being  %2  in.  to  J^  in.  The  positive  and  negative 
surfaces  are  kept  apart  by  thin  sheets  of  wood  or  rubber  known  as 
separators. 

Jars  and  Covers. — The  jars  forming  the  cells,  Fig.  41  and  Fig.  48,  are 
made  of  hard  rubber,  designed  t3  resist  both  the  action  of  the  electrolyte 


LATES 


BRIDGED 
SUPPORT 


SEDIMENT 
SPACE 


RUBBER 
JAR 


FIG.  49. — Cut  away  section  of  storage  cell  showing  sediment  space  below  the  plates. 

and  the  mechanical  strains.  Bridged  supports,  Fig.  49,  are  molded  in  the 
bottom  of  each  jar  to  hold  the  plates  and  separators  off  the  bottom,  thus 
forming  a  sediment  chamber  below  for  catching  the  accumulation  of  any 
active  material  which  may  free  itself  from  the  plates. 

The  cover,  Fig.  50,  is  of  hard  rubber  with  an  opening  in  the  center 
for  the  vent  cap  and  an  opening  on  each  side  for  the  connecting  posts  of 


IGNITION  BATTERIES  31 

the  positive  and  negative  groups,  which  are  known  as  terminals.  The 
cover  also  provides  an  expansion  chamber  for  the  electrolyte. 

Battery  Box. — The  battery  box  is  made  of  hard  wood  thoroughly 
coated  with  an  acid  proof  paint.  The  cells  are  usually  sealed  in  place 
in  the  battery  box  by  pouring  a  sealing  pitch  compound  over  the  entire 
top.  This  prevents  any  vibration  of  the  jars  and  renders  the  top  of  the 
cells  dirt  and  leak  proof.  In  some  cases,  where  specially  designed  covers 
are  used,  only  the  individual  cell  tops  are  sealed.  This  adds  greatly  to 
the  ease  with  which  the  battery  can  be  taken  apart. 

It  is  absolutely  essential  that  the  battery  be  securely  held  in  position 
on  the  car.  For  this  purpose,  brackets  are  fitted  on  the  battery  case  to 
which  bolts  are  attached  to  hold  the  battery  firmly  in  position. 

M-ti>i$ings  of  the  Battery.- — For  convenience  in  connecting  the  battery, 
the  terminals  are  ordinarily  marked  either  with  Pos.  (  +  ),  or  a  red 
fiber  sleeve  on  the  positive  post,  and  with  Neg.  (  — ),  on  the  negative 
post.  This  marking  is  in  accordance  with  the  way  the  battery  discharges, 
the  current  leaving  the  positive  terminal  and  returning  to  the  negative. 


>  NEGATIVE  LEAD 


GAS  BUBBLES  AROUND 
NEGATIVE.  TERMINAL 

SALTWATER  OR 
BATTERY  ELECTROLYTE. 

FIG.  50. — Cover  for  battery  cell.     FIG.  51. — Method  of  determining  polarity  of  storage 

battery  terminals. 

It  is  also  customary  among  battery  manufacturers  to  make  the  posi- 
tive cable  connection  larger  than  the  negative.  If  the  terminals  are  not 
marked,  the  polarity  can  be  readily  determined  by  attaching  a  wire  lead 
(pronounced  leed)  to  each  terminal  and  inserting  the  two  free  ends  in  a 
glass  of  salt  water  or  battery  electrolyte,  whereupon  gas  bubbles  (hydrogen) 
will  be  noticed  to  form  around  the  negative  lead  as  in  Fig.  51. 

28,  Separators. — The  separators  play  a  very  important  part  in  the 
life  and  operation  of  the  battery  since  they  insulate  the  positive  and 
negative  plates  from  each  other  and  prevent  short  circuits  between  them. 
If  the  separators  become  cracked,  or  damaged  in  any  other  way,  per- 
mitting metallic  contact  between  the  plates,  the  battery  will  discharge 
internally  and  may  ultimately  become  useless.  Two  principal  kinds 
of  separators  are  used,  namely,  wood,  and  threaded  rubber. 

The  wood  separator,  Fig.  52,  is  made  of  specially  selected  wood, 
usually  basswood  or  cypress,  which  is  chemically  treated  to  remove  the 
acetic  acid  and  other  impurities  which  are  always  in  the  wood  and  which 
are  harmful  to  the  battery.  This  chemical  treatment  also  makes  the 


32 


AUTOMOTIVE  IGNITION  SYSTEMS 


wood  more  porous,  to  allow  ready  diffusion  of  the  electrolyte  through 
the  separator  pores  upon  the  charging  and  discharging  of  the  battery. 
Each  separator  is  grooved  on  one  side.  When  they  are  installed,  this 
grooved  side  should  be  placed  next 
to  the  positive  plate  with  the 
grooves  running  vertical  as  in  Fig. 
53.  The  purpose  of  these  grooves 
is  to  permit  the  gas  which  accumu- 
lates around  the  positive  plate, 


FIG.  52. — Wood  separator. 


FIG.  53. — Inserting   separators   in    battery 
element. 


which  is  the  more  active  plate,  to  escape  freely  to  the  surface.  The 
grooves  also  provide  a  passageway  for  any  active  material,  which  may 
free  itself  from  the  plate,  to  fall  to  the  sediment  space  below. 


FIG.  54. — Willard  threaded  rubber  separator. 

The  threaded  rubber  separator,  Fig.  54,  is  manufactured  by  the 
Willard  Storage  Battery  Company  and  is  used  exclusively  in  the  Willard 
battery.  From  Fig.  55,  which  shows  a  magnified  view  of  this  separator, 
it  will  be  seen  that  the  threads  run  through  the  separator  at  right  angles 
to  the  surface.  According  to  the  manufacturers,  there  are  196,000  of 


IGNITION  BATTERIES 


33 


these  threads  per  sq.  in.  The  theory  is  that  each  thread  acts  as  a  wick 
between  the  positive  and  the  negative  plates.  The  separator  is  thus  ren- 
dered porous,  due  to  the  capillary  attraction  of  the  threads.  Another 
feature  of  this  separator  is  that  it  does  not  carbonize  and  crack  upon 
drying  out  as  does  the  wood  separator.  On  this  account  the  life  of  the 
separator  and  battery  is  greatly  increased.  The  threaded  rubber  separator 
has  corrugations  which  correspond  to  the  grooves  of  the  wood  separator 
and  should  be  installed  in  a  similar  manner,  with  the  corrugations  running 
vertical. 

29.  The  Electrolyte. — The  electrolyte,  as  used  in  all  types  of  auto- 
mobile lead  storage  batteries,  consists  of  a  mixture  of  chemically  pure 


*•  J&  <*  A 
#»   ***   **• 


FIG.  55. — Microscopic  section  of  Willard  threaded  rubber  separator. 

sulphuric  acid  (H2SO4)  and  distilled  water,  the  proportion  being  about 
two  parts  of  acid  to  five  parts  of  water  by  volume.  The  proportion  of  water 
and  acid  should  be  such  that  the  density  of  the  solution  will  have  a  specific 
gravity  of  1.300  at  70°F. 

Specific  Gravity. — By  specific  gravity  is  meant  the  ratio  of  the  weight 
of  any  substance  compared  with  the  weight  of  an  equal  volume  of  pure 
water  at  normal  temperature  and  pressure.  Pure  water  is  considered  to 
have  a  specific  gravity  of  1,  usually  written  1.000  and  spoken  of  as  ten 
hundred.  One  pound  of  water  has  a  volume  of  approximately  one  pint. 
An  equal  volume  of  chemically  pure  sulphuric  acid  weighs  1.835  Ib.  It, 
therefore,  Jaas  a  specific  gravity  of  1.835  and  is  spoken  of  as  eighteen 
thirty-five. 


34 


AUTOMOTIVE  IGNITION  SYSTEMS 


PI U.  UP  TO 
THIS  POINT 


In  the  cells,  the  electrolyte  should  cover  the  tops  of  the  plates  from 
in.  to  3^  in.  at  all  times  to  prevent  injury  to  the  plates  and  separators. 

The  proper  level  of  the  solution  is 
shown  in  Fig.  56. 

30.  The  Hydrometer. — A  conven- 
ient way  of  testing  the  specific  gravity 
of  the  electrolyte  is  by  the  hydrometer 
syringe  as  shown  in  Fig.  57A.  This 
instrument  consists  of  a  large  glass 
tube  syringe  within  which  is  a  small 
elongated  glass  hydrometer  float  with 
a  vertical  cylinder  graduated  from 
1.100  to  1.300.  The  rubber  bulb  at  the 
top  is  used  to  draw  the  liquid  into  the 
instrument.  Normally,  the  hydrom- 
eter rests  on  the  bottom  of  the  tube 
but,  as  soon  as  a  liquid  with  a  specific 
gravity  greater  than  1.100  is  drawn 
into  the  syringe,  the  hydrometer  floats 
at  a  depth  according  to  the  specific  gravity  of  the  liquid.  The  gradua- 
tion on  the  scale  in  line  with  the  surface  of  the  electrolyte,  Fig.  57B,  is 


FIG.  56. — Section  of  storage  cell  showing 
proper  level  of  electrolyte. 


HA 

PULL 

I.2I05P.GR 


MOO 

7200 

^- 

7300. 

I 

^31 

FIG.  57 — The  syringe  hydrometer. 

the  reading  of  the  specific  gravity  of  the  solution.  For  convenience,  its 
reading  is  spoken  of  as  being  1150,  1200, 1280,  1300,  etc.,  instead  of  1.15, 
1.2,  1.28,  and  1.3  which  is  of  course  correct.  The  reading  on  the  scale  of 


IGNITION  BATTERIES  35 

Fig.  57B  is  1.280  or  twelve-eighty.     The  hydrometer  syringe  is  also  used 
for  adding  water  to  the  cells. 

31.  Action  of  the  Lead  Storage  Cell  on  Discharge. — When  the  cell 
is  fully  charged,  the  electrolyte  has  a  density,  or  specific  gravity,  of 
1.275  to  1.300;  the  active  material  on  the  positive  plates  being  peroxide 
of  lead  and  on  the  negative  plates  pure  spongy  metallic  lead.  The  volt- 
age between  the  positive  and  negative  groups  is  from  2.1  to  2.2  volts. 
Consequently,  if  the  cell  terminals  are  connected  through  an  electric 
circuit,  such  as  the  ignition  system,  lighting  system,  or  starting  motor, 
current  will  flow  due  to  this  voltage.  As  the  cell  discharges,  chemical 
action  takes  place  between  the  sulphuric  acid  in  the  electrolyte  and  the 
lead  in  the  plates,. changing  the  lead  peroxide  of  the  positive  plates  and  the 
pure  spongy  metallic  lead  of  the  negative  plates  into  sulphate  of  lead.. 
This  lead  sulphate  is  formed  in  the  same  way  that  copper  sulphate  is 
formed  when  sulphuric  acid  is  dropped  on  a  copper  wire  terminal  and  in 
the  same  way  that  iron  sulphate  is  formed  when  sulphuric  acid  is  dropped 
on  the  iron  work  of  the  car.  In  cases  of  this  kind,  it  will  always  be  noticed 
that  the  amount  of  sulphate  formed  is  out  of  all  proportion  to  the  quantity 
of  metal  eaten  away.  In  the  same  manner,  when  the  sulphuric  acid  of 
the  electrolyte  combines  with  the  lead  in  the  plates  to  form  lead  sulphate, 
the  volume  is  increased  so  as  to  fill  completely  the  pores  of  the  active 
material  when  the  cell  is  completely  discharged.  This  makes  it  difficult 
for  the  charging  current  to  reach  all  parts  of  the  active  material,  and 
accounts  for  the  manufacturer's  instructions  never  to  discharge  the  bat- 
tery below  a  certain  point. 

As  the  discharge  progresses,  the  electrolyte  becomes  weaker,  due  to 
the  amount  of  acid  absorbed  by  the  active  material  of  the  plate  in  the 
formation  of  lead  sulphate,  which,  as  previously  explained,  is  a  compound 
of  sulphuric  acid  and  lead.  This  lead  sulphate  continues  to  increase 
in  bulk,  filling  the  pores  of  the  plates  eventually  to  such  an  extent  that 
the  free  circulation  of  the  acid  is  retarded.  Since  the  acid  cannot  reach  the 
active  material  of  the  plates  fast  enough  to  maintain  the  normal  action, 
the  battery  becomes  less  active.  This  is  indicated,  if  tested  at  intervals 
by  a  low  reading  voltmeter,  by  a  rapid  falling  off  in  the  voltage.  Starting 
at  slightly  over  2  volts  per  cell  (the  battery  being  fully  charged),  this 
voltage  is  maintained  at  normal  discharge  rates  with  but  a  slight  drop 
until  the  lead  sulphate  begins  to  fill  the  plate.  When  this  occurs,  the 
voltage  gradually  drops  to  1.8  volts  per  cell,  and  from  this  point  on  drops 
very  rapidly.  A  voltage  of  1.7  per  cell  indicates  practically  complete 
discharge;  also,  that  the  plates  of  the  cell  are  filled  with  lead  sulphate, 
and  that  the  battery  should  be  placed  on  charge  immediately. 

During  the  normal  discharge,  the  amount  of  acid  used  from  the 
electrolyte  will  cause  the  gravity  of  the  solution  to  drop  from  100  to  150 
points,  so  that  if  the  hydrometer  shows  a  reading  of  1.280,  when  the  cell 


36  AUTOMOTIVE  IGNITION  SYSTEMS 

is  fully  charged,  it  will  indicate  but  1.130  to  1.180  when  it  is  exhausted 
or  completely  discharged.  The  electrolyte  is  then  very  weak;  in  fact,  it  is 
little  more  than  pure  water,  since  practically  all  of  the  available  acid 
has  been  combined  with  the  active  material  of  the  plates.  Toward  the 
end  of  the  discharge,  the  electrolyte  becomes  so  weak  that  it  is  no  longer 
capable  of  producing  current  at  a  rate  sufficient  for  any  practical  purpose. 

32.  Action  of  the  Lead  Storage  Cell  on  Charge. — The  action  of  the 
cell  on  charge  consists  of  a  reversal  of  the  process  which  takes  place  when 
the  cell  discharges.  This  is  accomplished  by  sending  a  direct  current 
through  the  cell  in  a  charging  direction  which  is  opposite  in  direction  to  the 
current  flow  when  the  cell  discharges ;  namely,  in  at  the  positive  terminal 
and  out  at  the  negative  terminal.  When  the  charging  current  is  sent 
through  the  cell,  the  action  is  as  follows:  The  sulphuric  acid,  which  was 
absorbed  by  the  plates  on  discharge,  forming  lead  sulphate,  is  forced  out 
of  the  plates  back  into  the  electrolyte  thus  raising  the  specific  gravity. 
At  the  same  time  the  lead  sulphate  on  both  plates  (caused  by  the  sulphur 
in  the  acid  combining  with  the  lead)  is  converted  back  to  peroxide  of 
lead  in  the  positive  plates,  and  into  spongy  metallic  lead  in  the  negative 
plates.  When  practically  all  of  the  acid  has  been  transferred  from 
the  plates  to  the  electrolyte  and  the  sulphate  converted  back  into  its 
original  form,  the  cell  is  said  to  be  fully  charged  and  should  then  show  a 
specific  gravity  of  1.275  to  1.300  and  a  voltage  of  about  2.2  volts  on  open 
circuit. 

When  the  cells  are  completely  charged,  the  charging  current  can  do  no 
more  useful  work.  Its  only  effect  then  will  be  to  convert  particles  of 
water  in  tr.e  electrolyte  to  hydrogen  and  oxygen  gas  which  will  bubble  up 
violently  and  thereby  indicate  that  the  battery  is  nearing  a  full  state  of 
charge.  On  the  other  hand,  if  the  elements  of  the  cells  do  not  receive 
sufficient  charge,  the  sulphate  may  harden  to  such  an  extent  as  to  be 
very  difficult  to  remove  from  the  plates.  Furthermore,  if  the  battery  is 
allowed  to  remain  in  an  uncharged  condition,  a  denser  and  harder  sulphate, 
which  is  even  more  difficult  to  remove,  will  form  on  the  plates.  This 
hardening  of  the  sulphate,  commonly  known  as  sulphation,  takes  place 
to  some  extent  even  when  the  battery  is  considered  fully  charged.  It  is 
advisable,  therefore,  to  charge  the  battery  immediately  after  a  discharge 
and  about  once  a  month  when  out  of  service,  even  though  it  is  considered 
fully  charged. 

33.  Heat  Formed  on  Charge  and  Discharge. — When  the  cell  is 
charged  or  discharged,  the  chemical  reactions  due  to  the  passage  of  the 
current  through  the  electrolyte  cause  heat  to  be  generated.  This  heat 
does  not  become  injurious  until  the  temperature  rises  to  about  105°F., 
and  it  may  rise  to  110°F.  or  even  higher  for  a  brief  period  of  time  without 
injury  to  the  plates.  It  is  not  considered  advisable,  however,  to  charge 
a  battery  for  any  length  of  time  after  the  temperature  has  risen  to  105°F. 


IGNITION  BATTERIES  37 

The  battery  should  either  be  taken  off  charge  and  allowed  to  cool  or  the 
charging  rate  should  be  reduced. 

34.  Evaporation  of  Water. — The   water  in  the  "electrolyte  evapo- 
rates slowly  due  to  the  heat  formed  on  charge  and  discharge  and  also  due 
to  the  gassing  on  overcharge.     The  sulphuric  acid,  however,  does  not 
evaporate  and,  consequently,  the  solution  becomes  denser.     This  loss  of 
water  due  to  evaporation  must,  therefore,  be  made  up  by  adding  only  pure 
water.     The  amount  of  evaporation  depends  on  the  temperature  and 
on  the  amount  of  work  done  by  the  battery,  and  is  a  varying  quantity.     A 
safe  rule  to  follow  is  to  replace  the  water  every  week  in  summer  and  every 
two  weeks  in  winter,  during  ordinary  use  of  the  car.     If  the  car  is  out  of 
service,  water  should  be  added  once  every  two  weeks  in  summer  and  once 
a  month  in  winter  before  it  is  given  a  refreshing  charge.     During  cross- 
country touring  it  is  good  practice  to  add  distilled  water  every  200  miles 
of  travel,  or  once  a  day.     The  hydrometer  syringe  may  be  used  for  adding 
the  water.     Enough  water  should  be  added  to  keep  the  level  of  the  elec- 
trolyte at  all  times  up  to  the  bottom  of  the  inside  cover,  or  %  in.  to  %  in. 
above  the  tops  of  the  plates  as  shown  in  Fig.  56.     The  cells  should  never 
be  filled  above  this  level.     The  electrolyte  expands  when  charging,  due 
both  to  the  increase  in  temperature  and  to  the  gas  bubbles  which  rise 
from  the  plates;  therefore,  space  must  be  allowed  for  expansion.     The 
battery  if  filled  too  full  will  run  over,  resulting  not  only  in  loss  of  electro- 
lyte, but  in  the  eating  away  of  the  battery  box  and  serious  corrosion  of 
the  battery  terminals  and  connectors.     Discharge  circuits  may  also  result 
from  the  film  of  electrolyte  remaining  on  the  top  of  the  battery. 

35.  Necessity  of  Adding  Pure  Water. — Only  absolutely  pure  water, 
such  as  distilled  water,  should  be  used  in  filling  the  battery.     Distilled 
water  is  obtained  by  boiling  water,  catching  the  steam  that  comes  off, 
and  condensing  it  into  a  liquid.     Distilled  water  can  usually  be  obtained 
at  any  drug  store  or  garage  and  must  be  kept  in  an  acid-proof  vessel.     A 
common  way  of  storing  it  is  in  a  glass  bottle  or  jug.     Water  which  has 
merely  been  boiled  should  not  be  used.     If  distilled  water  is  hard  to 
obtain,  melted  artificial  ice,  or  filtered  rain  water  which  has  not  come  into 
contact  with  iron  pipes  or  tin  roofs,  may  be  used.     A  common  way  of 
collecting  the  latter  is  to  catch  the  rain  directly  in  an  earthenware  jar 
set  out  after  it  has  been  raining  for  about  5  or  10  minutes.     This  is  to  in- 
sure that  there  are  no  impurities  in  the  form  of  gases  and  small  solid  parti- 
cles taken  into  the  water  on  its  journey  from  the  clouds.     The  use  of 
spring,  river,  hydrant,  or  well  water  should  be  avoided  as  these  are  liable 
to  contain  iron  or  other  substances  detrimental  to  the  life  of  the  battery. 

36.  Storage  Battery  Testing. — Due  to  the  action  which  takes  place 
in  the  battery  cells  upon  discharge  (the  acid  of  the  electrolyte  combining 
with  the  active  material  in  the  plates  forming  lead  sulphate) ,  the  specific 
gravity  change  of  the  electrolyte  will  be  directly  in  proportion  to  the 


38 


AUTOMOTIVE  IGNITION  SYSTEMS 


state  of  charge  of  the  battery.  Thus  by  merely  testing  the  gravity  of 
the  electrolyte  with  a  hydrometer  the  exact  state  of  charge  of  the  battery 
can  at  once  be  determined,  providing  there  has  been  no  loss  of  electrolyte 
through  spilling,  and  that  no  acid  or  other  liquid  has  been  added  by  persons 
not  familiar  with  battery  principles  in  an  attempt  either  to  charge  the 
battery  or  to  keep  it  from  freezing.  If  it  is  known  that  the  battery  has 
been  so  treated,  the  voltage  of  each  cell  should  be  taken  with  a  low-reading 
voltmeter  to  check  the  hydrometer  readings.  When  fully  charged,  each 
cell  should  show  a  specific  gravity  of  1.280  to  1.300  and  about  2.2  volts 
per  cell.  The  following  table  gives  the  state  of  charge,  also  the  freezing 
temperature  of  the  storage  battery  at  different  specific  gravities.  It  will 


Specific  Gravity 

Approximate  Voltage 
Per  Cell 

Condition  of  Battery 

Freezing  Point  in  Degrees 
Fahrenheit 

1  .  275  to  1  .  300 

2.2 

Fully  charged 

90  degrees  below  zero 

1.260 

2.1 

%  charged 

60  degrees  below  zero 

1.210 

2.0 

Yz  charged 

20  degrees  below  zero 

1.160 

1.9 

Y±  charged 

Zero 

1  .  120  or  below 

1  .  8  or  less 

Completely  discharged 

20  degrees  above  zero 

be  noted  that  the  freezing  point  of  electrolyte  depends  upon  its  specific 
gravity  and  the  condition  of  battery  charge.  Therefore,  to  prevent  a 
battery  from  freezing,  it  should  be  kept  in  a  fully  charged  condition. 

37.  Variations  in  Cell  Readings. — If  the  specific  gravity  in  any  cell 
tests  more  than  25  points  lower  than  the  other  cells  in  a  battery,  it  is  an 
indication  that  this  cell  is  out  of  order.  One  reading  to  determine  the 
specific  gravity  of  a  cell  is  not  sufficient.  Several  readings  should  be 
taken  and  the  average  determined.  Variations  in  the  readings  of  differ- 
ent cells  may  be  due  to  short  circuits  inside  one  or  more  of  the  cells; 
putting  too  much  water  in  the  cell,  causing  the  electrolyte  to  overflow; 
or  to  loss  of  electrolyte  due  to  a  cracked  or  leaky  jar. 

Low  specific  gravity  in  one  or  more  cells  can  very  often  be  brought  up 
by  driving  the  car  (using  starter  and  lights  sparingly).,  or  charging  by 
means  of  the  generator  with  the  engine  running  idle,  in  which  case  read- 
ings ought  to  be  taken  at  frequent  intervals.  If  the  specific  gravity  in 
any  cell  does  not  come  up  to  at  least  1.260  after  the  other  cell  readings 
indicate  that  the  battery  is  fully  charged,  it  is  an  indication  that  the  low 
cell  is  in  need  of  internal  adjustment.  This  can  only  be  done  by  an  experi- 
enced battery  repairman. 

Most  battery  troubles  can  be  traced  to  the  electrolyte  becoming  too 
low  in  the  cells.  The  effect  of  this  is  to  weaken  the  battery,  thus  per- 
mitting it  to  be  more  easily  discharged,  and  freo1uently  causing  harmful 
sulpha tion  of  the  plates  and  injury  to  the  separators.  This  may  also 
allow  the  plates  to  come  together,  causing  internal  short  circuits.  It  is 


IGNITION  BATTERIES  39 

very  important,  therefore,  that  pure  distilled  water  be  added  regularly 
to  all  cells  in  order  to  keep  the  electrolyte  up  to  the  level  specified  by  the 
manufacturer. 

If  the  battery  does  not  regain  its  full  power  and  efficiency  within  one  or 
two  days  after  continuous  charging  on  the  car  as  explained  above,  it  is 
an  indication  that  the  battery  is  badly  sulphated,  or  has  some  other 
internal  trouble.  In  such  condition  the  battery  should  receive  immediate 
attention  from  a  competent  battery  man,  otherwise  it  may  be  entirely 
ruined.  A  frequent  cause  for  the  electrolyte  being  low  in  one  or  more  cells 
is  the  presence  of  a  cracked  or  leaky  jar.  If  one  cell  needs  more  frequent 
addition  of  water  than  the  other  cells,  it  is  a  good  indication  that  the 
jar  leaks.  This  condition  calls  for  immediate  action,  as  the  trouble  can 
very  easily  be  corrected  if  the  battery  is  taken  to  a  service  station  at 
once  and  a  new  jar  installed.  If  the  cracked  or  leaky  jar  is  not  im- 
mediately replaced,  the  cell  will  be  totally  ruined  and  very  likely  the 
entire  battery  seriously  damaged,  if  left  in  service.  Jars  are  frequently 
broken  due  to  the  battery  hold-down  bolts  or  clips  coming  loose,  allowing 
the  battery  to  jolt  around;  or  to  freezing  of  the  electrolyte  in  cold  weather. 
38.  Variation  in  Hydrometer  Readings  Due  to  Temperature  Changes. 
All  the  definite  figures  given  in  hydrometer  readings  are  based  on  the 
normal  temperature  of  70°F.  for  the  electrolyte.  This  refers  to  the 
temperature  of  the  liquid  itself,  and  not  to  the  temperature  of  the  sur- 
rounding atmosphere.  The  weather  might  be  freezing  cold  and  yet  the 
temperature  of  the  liquid  solution  in  the  battery  might  be  normal  or 
above,  either  from  the  heat  of  the  engine  or  because  the  battery  was  being 
vigorously  charged. 

The  temperature  of  a  battery  may  be  readily  measured  with  a  dairy 
thermometer  or  a  special  inexpensive  battery  thermometer  intended  for 
this  purpose.  The  thermometer  is  inserted  through  the  vent  plug-hole 
in  the  liquid  in  the  same  way  as  a  hydrometer.  The  rule  in  making 
temperature  correction  is  that  for  every  3°  above  70°F.,  0.001  be  added 
to  the  hydrometer  reading;  and  for  every  3°  below  70°F.,  0.001  be  sub- 
tracted from  the  observed  reading.  For  example:  If  the  temperature 
at  the  end  of  charge  is  120°F.  and  the  observed  gravity  reading  is  1.260, 
the  corrected  reading  is  determined  as  follows: 

120°  -  70°       =  50° 

50°  -5-3°         =  17°(approximately) 

17°  X  0.001    =  0.017° 

Corrected  reading:  1.260°  +  0.017°  =  1.277°. 
Again,  if  the  reading  at  0°F.  is  1.210,  then 

70°  -  0°          =  70° 

70°  -=-3°          =  23°  (approximately) 

23°  X  0.001    =  0.023° 
Corrected  reading:  1.210°  -  0.023°  =  1.187° 


40  AUTOMOTIVE  IGNITION  SYSTEMS 

From  the  above  it  can  be  seen  that  the  temperature  must  be  taken 
into  consideration,  otherwise  the  hydrometer  reading  will  be  misleading. 
It  is  usually  unnecessary  to  make  allowance  for  temperature  variations, 
but  it  is  well  to  bear  them  in  mind,  particularly  in  the  case  of  a  battery 
which  has  been  giving  trouble. 

Another  thing  to  remember  in  this  connection  is  that  in  hot  weather, 
if  the  temperature  of  the  liquid  is  more  than  20°  in  excess  of  the  tempera- 
ture of  its  immediate  surroundings,  the  battery  is  possibly  being  over- 
charged or  being  charged  at  too  high  a  rate,  or  is  in  a  bad  condition. 
This,  however,  cannot  be  given  as  a  positive  rule.  In  theory,  the  tem- 
perature of  the  liquid  in  a  battery  should  never  exceed  105°F.  as  high 
temperatures  have  an  injurious  effect  and  tend  to  shorten  the  life  of  the 
battery;  but  as  long  as  batteries  are  carried  in  locations  subjected  to 
engine  heat,  and  used  on  automobiles  in  hot  climates,  ideal  conditions 
do  not  exist  and  the  battery  must  get  along  as  well  as  it  can. 

39.  Capacity  of  a  Storage  Battery. — The  amount  of  current  that  a 
cell  will  produce  on  discharge  is  known  as  its  capacity,  and  is  measured 
in  ampere-hours.  It  is  impossible  for  a  cell  to  discharge  as  much  current 
as  was  required  to  charge  it,  the  efficiency  of  the  average  cell  of  modern 
type  when  in  good  condition  being  80  to  85  per  cent.,  or  possibly  a  little 
higher  when  at  its  best,  which  is  after  five  or  six  discharges.  In  other 
words,  if  100  ampere-hours  are  required  to  charge  a  battery,  only  80  to 
85  ampere-hours  can  be  discharged  from  it.  This  ampere-hour  capacity 
of  the  cell  depends  upon  the  area  of  the  plates  and  the  number  of  plates 
in  the  cell. 

The  capacity  of  the  cell  as  expressed  in  ampere-hours  is  based  on  its 
normal  discharge  rate.  A  100  ampere-hour  battery  will  produce  current 
at  the  rate  of  one  ampere  for  practically  one  hundred  hours  or  more,  two 
amperes  for  fifty  hours,  or  five  amperes  for  twenty  hours,  but  as  the  dis- 
charge rate  is  increased  beyond  a  certain  point,  the  capacity  of  the  bat- 
tery falls  off;  consequently,  it  would  not  produce  50  amperes  of  current 
for  2  hours.  This  is  because  of  the  fact  that  a  heavy  discharge  produces 
lead  sulphate  so  rapidly  and  in  such  large  quantities  that  it  fills  the 
pores  quickly  and  prevents  further  access  of  the  acid  to  the  active  ma- 
terial. Although  the  battery  will  not  produce  50  amperes  of  current  for 
two  hours  on  continuous  discharge,  it  will  be  capable  of  a  discharge  as 
great  or  considerably  greater  than  this  if  allowed  periods  of  rest  between. 
On  open  circuit,  the  storage  battery  recuperates  very  rapidly.  It  is 
for  this  reason  that  when  trying  to  start  the  engine  the  starting  switch 
should  never  be  kept  closed  for  more  than  a  few  seconds  at  a  time.  Ten 
trials  of  ten  seconds  each  with  a  half  minute  interval  between  them 
cause  the  battery  to  become  much  less  exhausted  than  if  the  engine 
is  turned  over  steadily  for  a  minute  and  forty  seconds. 


IGNITION  BATTERIES 


41 


40.  Battery  Charging. — When  batteries  are  charged  from  an  outside 
source,  only  direct  current  should  be  used.  It  is  not  possible  to  charge 
batteries  from  an  alternating  current  supply  without  an  apparatus,  either 
a  motor-generator  or  some  other  form  of  rectifier,  to  convert  the  alternating 
current  into  direct  current. 

In  charging,  the  positive  wire  of  the  charging  circuit  must  always  be 
connected  to  the  positive  (+)  terminal  of  the  battery.  If  this  is  reversed, 
serious  injury  may  result  to  the  battery.  The  charging  wires  may  be 
tested  for  polarity  either  by  using  a  voltmeter  or  by  immersing  the  ends 
of  the  wires  in  a  glass  of  water  to  which  a  few  drops  of  acid  or  a  little  salt 
have  been  added,  when  excessive  bubbles  will  form  on  the  negative  wire. 

In  charging  from  a  110-volt  direct-current  supply  it  is  necessary  to 
introduce  either  a  rheostat  (an  adjustable  resistance  unit),  Fig.  58,  or  a 
bank  of  lamps,  Fig.  59,  in  series  with  the  battery  in  order  to  regulate  the 
flow  of  charging  current.  When  using  a  lamp  bank  to  regulate  the  rate 


BATTERIES  TO  BE  CHARGED 


SWITCH 


FIG.  58. — Charging  batteries  from  110-volt  D.C.  supply,  using  rheostat  for  resistance. 

of  current,  as  in  Fig.  59,  110-volt  32  candlepower  carbon  filament  lamps 
should  be  used.  These  lamps  should  be  connected  in  parallel  with  each 
other,  and  the  combination  connected  in  series  with  the  battery.  With 
this  arrangement,  each  lamp  will  permit  about  one  ampere  of  charging 
current  to  pass  through  the  battery  so  that  the  number  of  lamps  in  use 
will  be  approximately  equal  to  the  number  of  amperes  of  current  to  be 
used  in  charging.  The  charging  rate  may  be  adjusted  by  turning  the 
lights  off  or  on,  or  by  moving  the  rheostat  handle  until  the  ammeter 
shows  the  proper  reading. 

Where  more  than  one  battery  is  to  be  charged  at  a  time,  the  batteries 
should  be  connected  in  series;  that  is,  the  positive  terminal  of  one  battery 
should  be  connected  to  the  negative  terminal  of  the  adjoining  battery. 
Rubber  covered  copper  wire  (No.  14  or  larger)  cut  in  lengths  of  about  18 
in.  should  be  used  to  connect  batteries  in  this  manner.  The  wire  is 
connected  to  the  terminals,  either  by  attaching  clips  to  the  ends  of  the 


42 


AUTOMOTIVE  IGNITION  SYSTEMS 


wires,  or  by  twisting  the  wire  around  the  terminals.  Care  should  be 
taken  to  see  that  a  good  contact  is  made  without  damaging  the  terminals. 
The  total  voltage  of  a  combination  of  batteries  is  the  sum  of  all  the 
cells  in  the  circuit  multiplied  by  the  voltage  of  each  cell  (2  volts).  In 
charging  batteries,  each  cell  requires  2.5  volts;  therefore,  care  should  be 
taken  to  see  that  the  total  voltage  required  for  charging  all  the  cells 
does  not  equal  or  exceed  the  operating  voltage  of  the  generator.  Should 
the  total  voltage  of  the  cells,  while  on  charge,  equal  the  voltage  of  the 
generator,  no  current  will  pass  through  the  battery.  Should  the  total 
voltage  of  the  cells  exceed  the  voltage  of  the  generator,  the  batteries  will 
discharge  themselves  through  the  generator.  When  charging  several 
batteries  in  series,  care  should  be  taken  to  see  that  the  charging  rate 
does  not  exceed  the  maximum  rate  of  the  battery  requiring  the  lowest 
charging  current. 


[  IIP  V. -DC.  SUPPLY 
AMMETER 


FUSES 


SWITCH 


ATT  EWES   TO  BE  CHARGED 


FIG.  59. — Charging  batteries  from  110- volt  D.C.  supply,  using  lamps  for  resistance. 

The  charging  rate  of  most  batteries  is  marked  on  the  name  plate; 
in  fact,  two  rates,  start  and  finish,  are  usually  given.  The  reason  for 
this  is  that  it  is  much  better  for  the  battery  if  the  charging  rate  is  re- 
duced when  approaching  a  full  state  of  charge,  to  avoid  excessive  heat- 
ing and  evaporation  of  the  electrolyte.  If  the  charging  rates  are  not 
marked  on  the  battery,  a  safe  charging  rate  at  the  start  would  be  about 
10  per  cent,  of  the  rated  ampere-hour  capacity,  and  5  per  cent,  of  this 
rating  to  finish.  In  the  case  of  an  80  ampere-hour  battery,  the  charg- 
ing rate  at  the  start  should  be  10  per  cent,  of  80  or  8  amp.  and  at  the  finish 
5  per  cent,  of  80  or  4  amp.  If  the  ampere-hour  capacity  is  not  known, 
the  charging  rate  at  the  start  may  be  8  to  10  amp.,  but  should  be  re- 
duced to  a  lower  rate  if  any  of  the  cells  show  signs  of  excessive  heating 
or  gassing. 

41.  Detailed  Instructions  for  Battery  Charging. — Before  placing  the 
battery  on  charge,  or  removing  the  vent  plugs  (or  caps),  the  entire 
top  of  the  battery  should  be  thoroughly  cleaned  off  to  prevent  any 


IGNITION  BATTERIES  43 

dirt  or  impurities  from  falling  into  the  cells.  If  any  of  the  cells  or  out- 
side battery  parts  are  corroded,  the  corrosion  should  be  cleaned  off 
with  a  solution  of  ordinary  washing  soda  and  water,  applied  with  a 
clean  cloth  or  sponge.  The  vent  plugs  (or  caps)  should  then  be  re- 
moved and  not  replaced  until  the  battery  is  removed  from  the  charging 
circuit,  unless  a  special  type  of  filler  tube  is  used  which  requires  the 
plug  to  remain  in  place  while  the  battery  is  charging.  In  this  case, 
the  plug  is  removed  only  when  it  is  necessary  to  take  a  hydrometer 
reading  or  to  add  distilled  water.  Distilled  water  should  be  added  to  all 
the  cells  in  sufficient  quantities  to  bring  the  electrolyte  up  to  the  proper 
level,  which  in  most  batteries  is  J^  in.  above  the  top  of  the  plates. 

The  battery  is  placed  on  charge  at  the  start  rate  specified  on  the 
name  plate  and  the  voltage  of  each  cell  tested  immediately.  The 
voltage  and  hydrometer  readings  of  each  cell  should  be  made  every 
hour.  The  charge  at  the  start  rate  should  continue  until  one  or  more  of 
the  cells  are  gassing  vigorously  and  the  voltage  of  each  cell  reads  2.5 
or  higher  during  charge.  The  charging  rate  should  then  be  reduced  to 
the  finish  rate  and  charging  continued  at  this  rate  until  the  battery 
is  fully  charged. 

A  battery  is  fully  charged  when,  with  the  current  flowing  at  the 
finish  rate,  all  cells  are  gassing  vigorously;  the  voltage  and  specific 
gravity  of  each  cell  have  stopped  rising  and  have  been  constant  for 
one  hour;  the  voltage  will  read  2.4  or  higher  per  cell  while  charging,  but 
will  drop  to  2.25  immediately  upon  removing  the  battery  from  charge, 
after  which  it  will  gradually  drop  to  about  2.1  volts  per  cell;  and  the 
specific  gravity  of  each  cell  tests  between  1.275  and  1.300. 

Although  it  is  always  advisable  to  use  a  voltmeter  in  battery  charg- 
ing it  is  not  absolutely  essential.  When  a  voltmeter  is  not  used,  the 
start  rate  should  be  continued  until  the  battery  is  gassing  vigorously. 
The  rate  should  then  be  reduced  to  the  finish  rate  and  charging  con- 
tinued until  the  specific  gravity  of  all  the  cells  has  stopped  rising  and 
remains  constant  for  one  hour.  If  the  specific  gravity  rises  above  1.300, 
while  the  battery  is  on  charge,  part  of  the  electrolyte  should  be  drawn 
from  the  cells  and  enough  distilled  water  added  to  reduce  the  specific 
gravity  to  1.285.  If,  on  the  other  hand,  the  specific  gravity  will  not 
come  up  to  1.275  by  continuous  charging,  it  indicates  that  there  is 
insufficient  acid  in  the  electrolyte.  The  specific  gravity  should  be 
corrected  by  removing  some  of  the  electrolyte  from  the  defective  cell  and 
replacing  it  with  a  like  amount  of  electrolyte  of  1.350  to  1.400  sp.  gr. 
Pure  acid  should  never  be  added  to  a  battery  as  it  will  gas  and  heat 
violently  and  will  damage  the  plates  and  separators.  Figure  60  shows  the 
effect  on  wood  separators  by  filling  the  cell  with  too  strong  an  acid  solu- 
tion. After  the  specific  gravity  has  been  adjusted,  the  battery  should 
remain  on  charge  for  at  least  one  hour,  The  voltage  at  the  completion 


44 


AUTOMOTIVE  IGNITION  SYSTEMS 


of  the  charge  should  be  about  2.5  volts  for  each  cell,  but  this  will 
immediately  drop  to  approximately  2.2  volts  per  cell  making  the  voltage 
of  a  fully  charged  three-cell  battery  about  6.6  volts.  The  voltage,  how- 
ever, will  vary  slightly  with  the  temperature. 

Caution.- — Care  should  be  taken  to  keep  open  flames  away  from  a 
battery  which  is  or  has  been  charging  or  discharging.  The  gas  which 
accumulates  in  the  cells,  due  to  the  chemical  action,  is  combustible 
and  may  cause  sufficient  explosion  to  wreck  the  battery  and  injure 
the  operator. 

After  the  battery  has  been  removed  from  the  charging  line,  the  vent 
caps  should  be  screwed  tightly  into  place  and  the  battery  top  and  con- 
necting terminals  cleaned  with  water.  To  prevent  corrosion  of  the 


FIG.  60. — Effect  of  strong  electrolyte  on  wood  separator. 

battery  terminals  by  the  acid  they  should  be  greased  with  a  light  coat  of 
vaseline  or  soft  grease. 

42.  Sulphation. — When  a  storage  battery  is  discharging,  the  plates 
are  acted  upon  by  the  sulphuric  acid  in  the  electrolyte,  converting 
the  lead  peroxide  of  the  positive  plate  and  the  pure  sponge  lead  of  the 
negative  plate  into  a  lead  sulphate,  which  is  converted  back  into  its 
original  form  when  the  battery  is  recharged.  When  the  plates  are 
permitted  to  remain  in  a  discharged  condition,  the  lead  sulphate  grows 
into  a  hard,  white,  crystalline  formation,  which  closes  up  the  pores, 
destroying  the  active  area  of  the  plates.  This  formation  is  known  as 
sulphation.  Figure  61  shows  a  positive  group  of  a  battery  with  wood 
separators  that  has  been,  opera  ted  in  a  partially  discharged  condition 
for  somejength  of  time.  The  white  area  on  the  plate  indicates  the 
sulphation. 


IGNITION  BATTERIES 


45 


Sulphation  is  also  caused  by  low  electrolyte  or  because  the  cell 
has  not  been  filled  with  water.  If  water  is  not  added  at  regular  inter- 
vals to  replace  loss  through  evaporation,  the  electrolyte  level  will  soon 
fall  below  the  plate  tops,  causing  that  portion  of  the  plates  which  is 
exposed  to  the  air  to  sulphate  rapidly.  Figure  62  shows  a  sulphated 
condition  of  plates,  after  a  few  months'  use  (or  rather  misuse),  produced 
by  lack  of  water  and  by  allowing  the  solution  to  become  low  and  not 
cover  the  plates.  A  hard  white  sulphate  has  formed  on  the  top  half  of 
the  plates.  It  is  difficult  and  sometimes  impossible  to  recharge  and 
bring  back  to  normal  condition  a  plate  that  has  dried  out  and  has 
become  hard.  The  concentrated  condition  of  the  electrolyte  (only  the 
water  evaporates)  is  also  injurious  to  the  lower  half  of  the  plates  and 


FIG.  61. — Sulphation    of    battery    plates 
due  to  undercharging. 


FIG.  62. — Sulphation    due    to    underfilling 
of  battery. 


separators.  Sulphate  is  a  non-conductor  of  electricity;  therefore, 
it  is  quite  destructive  to  the  activity  of  the  plates  and  reduces  mate- 
rially the  ampere-hour  capacity  of  the  battery.  For  example,  in  a 
100  ampere-hour  battery  in  which  one  half  of  the  plate  area  is  sealed 
up  by  the  sulphation,  the  capacity  will  be  reduced  approximately  50 
per  cent,  and  the  battery  capable  of  no  more  work  than  a  battery  rated 
at  50  ampere-hour  capacity.  The  only  way  sulphation  can  be  removed, 
if  it  is  not  too  bad,  is  by  prolonged  charging  at  a  very  slow  rate,  usu- 
ally the  finish  rate  for  the  battery.  It  may  require  charging  for  several 
days  to  restore  it  to  a  fully  charged  condition. 

In  order  to  prevent  sulphation,  the  battery  should  be  kept  charged  and 
the  plates  well  covered  with  electrolyte. 


46 


AUTOMOTIVE  IGNITION  SYSTEMS 


43.  Effect  of  Overfilling. — The  effect  of  overfilling  a  battery  is 
well  illustrated  by  Fig.  63.  The  battery  should  be  filled  with  water- 
up  to  the  bottom  of  the  cover  tube,  or  %  in.  to  %  in.  above  the  top 
of  the  plates.  If  it  is  filled  above  this  point,  it  will  run  over  upon 
charging,  due  to  the  lack  of  space  for  expansion.  This  will  result  in 
a  loss  of  the  electrolyte  and  an  eating  away  of  the  battery  box  as  indi- 


FIG.  63. — Effect  of  over-filling  the  battery  cells. 

cated.     The  electrolyte  may  also  get  into  the  metal  case  and  eat  out 
the  bottom. 

44.  Corroded  Terminals. — Frequently,  the  terminals  and  connectors 
will  be  found  covered  with  a  greenish  deposit.  This  is  a  corrosion 
due  to  the  acid  fumes  which  are  constantly  passing  off  from  the  cells 


FIG.  64. — Effect  of  corrosion  on  battery  cable  terminals. 

and  attacking  the  metal  connectors.  Figure  64  shows  a  cable  terminal 
badly  corroded  by  the  splashing  or  spraying  of  electrolyte  on  the  bare 
cable  wires  where  insulation  has  been  stripped  off. 

The  eating  action  may  be  stopped  and  all  corrosion  removed  by 
soaking  the  parts  in  a  solution  of  bicarbonate  of  soda  (common  baking 
soda)  or  ammonia  and  brushing  them  with  a  stiff  brush,  after  which  they 


IGNITION  BATTERIES 


47 


should  be  wiped  dry.     Further  corrosion  will  be  prevented  by  covering 
the  parts  with  a  light  coat  of  vaseline  or  cup  grease. 

45.  Disintegrated  and  Buckled  Plates. — Overheating  of  the  plates, 
through  excessive  charging  or  discharging,  causes  them  to  warp  or 
buckle.  It  also  causes  disintegration  of  the  active  material,  especially 
in  the  positive  plates.  Figure  65  shows  w'hat  continuous  overcharging 
does  to  the  positive  plates.  It  softens  up  the'  material  and  causes  the 
battery  to  give  unusually  high  capacity  for.  a  short  time.  The  material 
then  begins  to  disintegrate  and  fall  out.  The  effect  is  about  the  same 
as  freezing.  In  order  to  determine  which  condition  has  existed  it  should 


FIG.  65. — Effect    on    battery    plates    of 
continuous  overheating. 


FIG.  66. — Buckled  battery  plates. 


be  remembered  that  overheating  usually  blackens  and  softens  the  wood 
separators. 

A  plate  is  especially  liable  to  buckle,  when  in  a  sulphated  condition,  if 
discharged  or  charged  at  a  high  rate.  The  sulphated  portion  of  the 
plate  does  not  expand  at  the  same  rate  as  the  active  area,  thus  causing 
unequal  expansion  and  a  warping,  sometimes  cracking,  of  the  grid.  A 
group  which  has  been  allowed  to  stand  discharged  at  a  low  point  for 
some  time,  then  charged  at  a  high'  rate  to  restore  its  energy,  is  shown  in 
Fig.  66.  On  account  of  the  hardness  of  the  plates  and  the  extra  resist- 
ance of  the  sulphate  formed  during  the  excessively  low  period  of  dis- 
charge the  plates  become  very  hot  and  being  only  slightly  flexible  or 


48 


AUTOMOTIVE  IGNITION  SYSTEMS 


elastic,  warp  or  buckle  when  expanded  by  heat.  Figure  66  shows  the 
difference  between  a  cell  continuously  overcharged  and  one  which  has 
been  undercharged  so  that  the  sulphation  has  become  hard.  Buckling 
also  causes  a  breaking  down  of  the  separators  and  often  results  in  cracking 
the  jar,  as  in  Fig.  67,  resulting  in  loss  of  the  electrolyte. 

To  avoid  overheating  and  buckling  of  the  plates,  the  following  pre- 
cautions should  be  taken: 

1.  Sulphation  should  be  prevented  by  keeping  the  battery  charged 
and  properly  filled. 

2.  The  generator  should  be  adjusted  to  charge  the  battery  at  the 
proper  rate. 

3.  The  starting  motor  should  not  be  operated  excessively. 

4.  The  car  should  not  be  propelled  with  the  starter. 


FIG.  67. — Cracked    jar    due    to    buckled 
plates. 


FIG.  68. — A  worn-out  battery  plate 
showing  the  active  material  fallen  out  and 
the  grid  exposed. 


5.  The  battery  temperature  should  be  watched  in  hot  weather,  and 
when  touring.  If  the  top  connectors  feel  warm  to  the  hand,  the  head- 
lights should  be  turned  "ON"  to  cut  down  the  battery  charging  rate. 

46.  Sediment. — When  a  battery  is  used,  a  deposit  known  as  sediment 
collects  in  the  bottom  of  the  jars,  due  to  the  gradual  wearing  away  of 
the  active  material  in  the  plates.  Figure  68  shows  a  worn-out  plate  from 
which  practically  all  the  active  material  has  fallen.  In  time,  this  sediment 
may  fill  up  the  sediment  or  mud  space,  causing  a  short  circuit  at  the  bottom 
of  the  plates.  In  this  event,  the  cell  must  be  dismantled  and  the  sedi- 
ment removed.  Broken  down  insulation  due  to  high  sediment  or  defec- 
tive separators  is  indicated  by  the  inability  of  a  cell  to  hold  a  charge  on 
open  circuit.  Other  indications  of  broken  down  insulators  are  undue 
heating  of  the  cells  upon  charging,  little  or  no  voltage  or  gravity  rise 


IGNITION  BATTERIES 


49 


after  a  prolonged  charge,  and  the  impossibility  of  making  the  cells  gas 
properly.  Such  a  cell  is  considered  dead  and  can  be  remedied  only  by 
dismantling  and  rebuilding  the  battery.  This  is  a  job  which  should  be 
undertaken  only  by  an  experienced  battery  repairman  as  it  involves 
lead  burning  usually  with  either  a  hydrogen  or  oxy-acetylene  flame,  an  art 
requiring  special  lead  burning  equipment,  and  much  practice. 

47.  Care  of  Storage  Batteries  in  Winter. — It  \\ill  be  noted  from  the 
table  on  page  38  that  the  freezing  point  of  electrolyte  depends  upon  its 
specific  gravity  and  the  condition  of  battery  charge.  Therefore,  to  pre- 
vent a  battery  from  freezing,  it  must  be  kept  in  a  fully  charged  condition. 
The  effects  of  freezing  are  clearly  shown  in  Fig.  69  and  Fig.  70. 


FIG.  69. — Effect   of  freezing   on   battery 
plates. 


FIG.  70. — Cracked     battery     jar     due 
freezing. 


If  it  becomes  necessary  to  add  water  to  the  battery  in  cold  weather, 
this  should  be  done  just  before  running  the  engine.  In  very  cold  weather, 
however,  it  is  better  to  start  the  engine  and  have  the  battery  charging 
before  the  water  is  added.  This  is  done  because  water,  being  lighter 
than  electrolyte,  remains  on  the  surface  of  the  liquid  in  the  cells  until 
circulated  and  mixed  by  the  charging  current:  If  water  is  added,  there- 
fore, and  the  battery  allowed  to  stand  for  a  time  without  charging,  there 
is  a  possibility  of  the  water's  freezing  on  the  surface  of  the  solution. 

48.  Conditions  Causing  the  Battery  in  the  Electrical  System  to  Run 
Down. — It  is  impossible  to  include  here  all  the  conditions  which  may 
cause  the  battery  in  the  electrical  system  to  run  down,  since  many  of  the 
causes  may  be  due  to  faults  in  the  starting  and  generating  system.  How- 


50  AUTOMOTIVE  IGNITION  SYSTEMS 

ever,  a  few  of  the  most  important  causes  are  given  to  assist  in  diagnosing 
battery  trouble  on  the  automobile. 

A  discharged  or  weak  condition  of  the  battery,  which  is  indicated  by 
feeble  ignition,  a  loss  in  cranking  power  of  the  starter,  dim  lights,  low 
specific  gravity,  etc.  may  be  attributed  to  one  of  the  following  causes: 

1.  Generator  either  not  charging  the  battery  or  charging  at  insufficient  rate. 

2.  Battery  plates  not  kept  properly  covered  with  electrolyte,  causing  sulphation  of 
the  plates. 

3.  Drain  on  battery  due  to  excessive  lamp  load  or  too  many  electrical  accessories 
not  intended  for  the  battery. 

4.  Engine  not  driven  fast  enough  to  charge  at  sufficient  rate. 

5.  Too  much  night  driving  with  full  lamp  load  on. 

6.  Excessive  use  of  the  starting  motor;  starting  switch  sticking. 

7.  Electrical  cut-out  not  operating  properly. 

8.  Battery  ignition  switch  left  on  with  engine  not  running. 

9.  Cracked  jar  causing  loss  of  electrolyte. 

10.  Broken  down  battery  insulation  due  to  high  sediment  or  defective  separators. 

11.  Loose  connections  on  generator,  cut-out,  or  battery. 

12.  Corroded  battery  terminals. 

13.  Overfilling,  causing  loss  of  electrolyte  and  short  circuits. 


CHAPTER  III 
THE  JUMP-SPARK  IGNITION  SYSTEM 

49.  Requirements  of  Automotive  Engine  Ignition. — The  internal 
combustion  engines  used  for  automobile,  truck,  tractor,  motor  boat,  and 
airplane  propulsion  at  the  present  time  depend  upon  some  form  of 
electrical  ignition  for  igniting  the  charge  of  fuel  within  the  engine  cylinder. 
This  is  accomplished  by  means  of  an  electric  spark  produced  inside  the 
cylinder  when  the  respective  piston  is  nearing  the  end  of  its  compression 
stroke. 

The  engines  used  on  automobiles,  trucks,  tractors,  •  and  airplanes 
operate  on  the  four-stroke  cycle  principle  in  which  four  strokes  of  the 
piston  are  required  to  complete  the  four  events  of  the  engine  cycle: 
namely,  the  suction  stroke  in  which  a  charge  of  fresh  gas  is  drawn  into 
the  cylinder;  the  compression  stroke  in  which  the  charge  of  gas  is  com- 
pressed into  the  upper  end  of  the  cylinder;  the  power  or  working  stroke  at 
the  beginning  of  which  the  gas  is  ignited ;  and  the  exhaust  stroke  during 
which  the  burned  gas  is  pushed  out  of  the  cylinder.  These  four  strokes 
are  completed  in  two  revolutions  of  the  flywheel.  Consequently,  one 
ignition  spark  is  required  for  each  cylinder  every  two  revolutions  of  the 
engine.  When  it  is  considered  that  many  of  the  modern  four-,  six-, 
eight-,  and  twelve-cylinder  engines  run  up  to  3,000  and  4,000  revolutions 
per  minute,  requiring  of  a  single  ignition  system  as  many  as  400  sparks 
per  second,  it  will  be  realized  that  the  proper  action  of  the  ignition  system 
in  supplying  a  spark  in  each  cylinder  at  the  proper  time  is  of  the  utmost 
importance. 

Another  type  of  internal  combustion  engine  used  to  some  extent  on 
motor  boats  and  for  small  stationary  installations  operates  on  the  two- 
stroke  cycle  principle,  in  which  but  two  strokes  of  the  piston  are  needed  to 
complete  the  events  of  the  engine  cycle.  In  this  type  of  engine  the  suc- 
tion stroke  and  the  exhaust  stroke  of  the  four-stroke  cycle  engine  are 
absent,  the  crank  case  of  the  engine  being  used  as  a  pump  to  force  the 
fresh  gas  into  the  working  end  of  the  cylinder.  The  entering  charge  of 
gas  blows  the  burned  gas  out  of  the  cylinder  through  a  port  in  the  cylinder 
wall  which  is  uncovered  by  the  piston  at  the  lower  end  of  its  stroke. 
This  engine  requires  one  spark  for  each  cylinder  every  revolution  of  the 
crankshaft,  but  due  to  the  fact  that  the  speed  of  the  two-stroke  cycle 
engine  is  limited  to  about  1,000  revolutions  per  minute,  the  total  number 
of  ignition  sparks  required  per  second  from  the  ignition  system  never 
reaches  the  maximum  mentioned  for  the  four-stroke  cycle  engine. 

51 


52  AUTOMOTIVE  IGNITION  SYSTEMS 

50.  Make-and-break  and  Jump -spark  Ignition.— Two  methods  of 
electrical  ignition  have  been  used;  namely,  the  make-and-break  and  the 
jump-spark.     The  latter  method,  however,  is  the  only  one  satisfactory 
for  high-speed  service,  the  make-and-break  system  being  used  chiefly 
on  low-speed  engines  with  a  high  compression  of  150  Ib.  per  sq.  in.  or 
over. 

In  the  make-and-break  method  of  ignition,  an  electric  current  of  low 
voltage,  furnished  either  by  a  battery  or  by  a  magneto,  is  made  and 
broken  by  a  contact  mechanism  known  as  an  igniter,  Fig.  71,  the  contact 
points  of  which  extend  into  the  combustion  chamber  of  the  engine 
cylinder.  The  igniter  mechanism  is  operated  by  a  push  rod  which  in 
turn  is  operated  by  a  cam  driven  by  the  crankshaft  at  one-half  engine 
speed.  This  mechanism  is  timed  so  as  to  effect  ignition  when  the  fuel 
charge  is  near  maximum  compression  or  when  the  piston  is  approximately 
on  head  end  dead  center  position.  The  spark  for  ignition  occurs  at  the 
instant  the  contacts  open,  and  is  caused  by  the  sudden  stoppage  of  the 
electric  current  in  combination  with  the  action  of  a  low-voltage  coil 
connected  in  the  circuit. 

In  the  jump-spark  ignition  system,  current  is  derived  either  from  a 
battery  or  from  a  magneto,  but  it  is  first  transformed  from  low  voltage  to 
high  voltage  by  means  of  an  induction  coil,  whereupon  the  high-voltage 
current  is  made  to  jump  the  points  of  a  spark  plug  inside  the  cylinder. 
The  spark  thus  created  sets  fire  to  the  combustible  gases. 

For  automotive  engine  ignition  the  make-and-break  method  is  no 
longer  used,  it  having  given  way  to  the  jump-spark  method  on  account 
of  the  greater  simplicity  and  many  advantages  of  the  latter.  However, 
owing  to  the  similarity  in  the  action  of  the  ignition  coils  used  in  both 
systems,  the  operation  of  the  make-and-break  coil  should  be  clearly 
understood. 

51.  The  Low-tension  Coil  for  Make-and-break  Ignition. — The  coil 
used  for  make-and-break  ignition  is  very  simple  in  construction  in  that 
it  consists  of  a  single  winding  of  insulated  copper  wire  wound  on  a  soft 
iron  core  as  shown  in  Fig.  71.     The  core  is  usually  made  of  a  bundle  of 
soft  iron  wire  so  that  it  will  magnetize  and  demagnetize  rapidly.     Such  a 
coil  is  usually  termed  a  kick  coil  for  the  reason  that,  if  a  current  through 
the  coil  is  suddenly  interrupted  by  breaking  the  circuit,  a  flashy  spark  of 
considerable  intensity  or  "kick"  will  occur  at  the  point  of  current  inter- 
ruption.    The  spark  thus  produced  occurs  between  the  igniter  points 
inside  the  cylinder  and  is  made  use  of  in  igniting  the  fuel  charge. 

The  large  flashy  spark  which  occurs  at  the  point  of  current  interrup- 
tion is  due  to  the  induction  of  a  voltage  and  a  current  in  the  winding  of 
the  coil  by  the  collapsing  lines  of  force  when  the  circuit  is  broken.  From 
a  study  of  Fig.  71  it  will  be  seen  that,  upon  the  demagnetizing  of  the  core, 
the  magnetic  lines  of  force  will  move  rapidly  toward  the  core  and  cut 


THE  JUMP-SPARK  IGNITION  SYSTEM 


53 


each  turn  of  wire  much  the  same  as  in  Fig.  24.  This  cutting  of  the  wire 
by  the  lines  of  force  will  set  up  a  whirl  of  magnetic  lines  around  each  turn 
of  wire  and  induce  a  voltage  in  the  coil  in  the  same  direction  as  the  original 
current  from  the  batteries.  This  induced  or  kick  voltage  of  the  coil  is 
in  series  with  the  battery  voltage  and  often  reaches  a  momentary  pres- 
sure of  200  to  300  volts,  depending  on  the  design  and  the  size  of  the  coil. 
Such  a  voltage  is  sufficient  to  break  down  for  an  instant  the  resistance 
of  the  air  gap  between  the  igniter  points,  when  the  circuit  is  broken,  thus 
permitting  the  induced  current  to  flow  across  this  gap  and  produce  a 
very  hot,  yellow,  flashy  spark. 


_ 


BATTERY  ,   IGNITER" 

FIG.  71. — Principle  of  the  low- tension  coil. 

The  action  of  a  kick  coil  may  be  compared  to  the  water  hammer  in  a 
water  pipe.  If  the  valve  is  closed  suddenly,  when  the  water  is  flowing, 
the  momentum  of  the  water  in  motion  will  produce  a  terrific  blow  on  the 
valve,  known  as  water  hammer.  The  instantaneous  pressure  produced 
by  the  water  hammer  may  be  several  times  that  of  the  ordinary  pressure 
of  the  water  which  set  up  the  motion  when  the  valve  was  open. 

52.  The  Induction  Coil. — When  the  current  for  automobile  ignition  is 
derived  from  the  dry  battery,  storage  battery,  low-tension  magneto,  or 
generator,  the  voltage  usually  ranges  from  6  to  12  volts.  This  voltage  is 
too  low  to  force  a  spark  to  jump  the  gap  between  the  spark  plug  points 
inside  of  the  engine  cylinder;  consequently,  the  low-voltage  current  must 
first  be  transformed  to  a  current  of  high  voltage  by  a  special  transformer 
known  as  an  induction  coil.  Induction  coils  may  be  of  either  the  vibrat- 


V  AUTOMOTIVE  IGNITION  SYSTEMS: 


ing  or  'ncin-vibrating  type,  but  in  either  case  the  general  construction  and 
principle  of  operation  are  the  same.  The  chief  difference  is  that  the 
vibrating  type  induction  coil  operates  with  a  timer  and  gives  a  shower  of 
sparks  at  the  plug,  .while  the .  non- vibrating  type  of  coil  operates  with  a 
breaker  and  gives  a  single  spark  at  the  plug.  The  non-vibrating  coil  is 
the  more  popular  for  automobile  ignition.  Its  application  to  a  jump- 
spark 'ignition  system  is  illustrated  in  Fig.  72. 

The  induction  coil  consists  essentially  of  a  primary  and  a  secondary 
winding,  ^bbth;  wound  on  a  core  of  soft  iron.  This  core  usually  consists 
of  a  bundle,  of  soft  iron  wires,  the  core  being  about  .J^  in.  to,  %  in.  in 
diameter  and  5  in.  to  6  in.  long.  The  wires  are  annealed  to  make  them  as 
soft  as  possible  so  that  the  core  will  magnetize  and  demagnetize  rapidly. 


INDUCTION,  COIL 


SPARK  PLUG 


SWITCH 
PRIMARY  WINDINQ'4^1 

(LARGE.  WIRE)         I.'.'1',' 

':;:.'!! 


SECONDARY 

(FINE  WIRE) 


GROUfJD  -*.. 


SOFT  IRON  CORt:<';r-v'- 

(COMPOSED  OF  BUNDLE 
OF  SOFT  IRON  WIRE5) 


CAM  DRIVEN  FROM  E 

AT  1  CRANK  SHAFT  SPEED''  |N5ULATwix  , 
TERMINAL   || 


CONDELNSER 


CIRCJIT  THROUGH  ENGINE  FRAME 
FIG.  72, — Jump-spark  ignition  with  breaker  and  non- vibrating  coil. 

The  primary  winding  which  is  connected  to  the  source  of  current 
supply  consists  usually  of  several  layers  of  insulated  copper  wire,  ranging 
in  size  from  No.  16  to  No.  20  B  &  S  gage.  The  wire  is  wound  around  the 
core  so'  as  to  make  it  an  electromagnet.  The  insulation  of  the  wire  usually 
consists  .of  layers  of  cotton  fiber,  though  in  some  cases  an  enamel  in- 
sulation is  used. 

The  secondary,  or  high-tension  winding,  to  which  the  spark  plug  is 
connected,  is  wound  outside  of  the  primary  coil  and  is  made  up  of  several 
thousand  turns  of  enameled  or  silk  covered  copper  wire,  usually  about  No. 
36;  B  &  S  gage.  This  winding  is  sometimes  made  up  of  many  layers,  each 
layer  running  the  entire  length  of  the  coil,  the  .layers  being  insulated 
from  each  other  by  paraffin  wax  paper.  In  another  type  of  construction, 
the  winding 'is  made  up  of  several  narrow  spools  or  " pancakes"  assembled 
-over'.'thb- primary  coil  with  suitable  insulation  between.  The  adjacent 


THE  JUMP-SPARK  IGNITION  SYSTEM  55 

ends  of  these  pancake  coils  are  connected  so  that  their  windings  are  in 
series. 

The  reason  for  this  construction  is  as  follows  :  The  secondary  winding 
of  an  induction  coil  used  for  gas-engine  ignition  produces,  at  times,  a 
pressure  of  10,000  to  20,000  volts.  This  means  that  the  quality  of  the 
insulation  and  construction  must  be  very  high  to  prevent  this  induced 
current  from  escaping  at  some  other  point  than  at  the  spark-plug  gap. 
The  normal  voltage  necessary  to  jump  the  spark-plug  points  under 
compression  and  with  the  points  properly  adjusted  is  usually  from  5,000 
Each  turn  of  the  winding  develops  its  share  of  the  voltage 


of  the  whole  coil.  In  coils  where  the  winding  is  made  in  long  layers,  the 
full  voltage  developed  exists  between  the  inner  and  outer  layers.  One 
can  see,  then,  that  there  is  a  chance  for  the  spark  to  leap  between 
layers,  which,  of  course,  must  be  prevented  by  high-quality  insulation. 
It  is  a  common  practice  to  run  a  layer  of  thin  waxed  paper  between  the 
layers  of  wire  and  to  impregnate  the  whole  winding  with  wax.  In  this 
way  the  coil  is  not  affected  by  dampness  and  there  is  less  chance  for  the 
winding  to  break  down  due  to  defective  insulation.  By  break  down  of 
the  secondary  winding  is  meant  a  flow  of  the  current  between  layers  of 
the  winding,  causing  an  arc  within  the  coil  instead  of  at  the  desired  point 
where  the  spark  is  wanted.  In  pancake  windings,  the  terminals  of  the 
secondary  coil  are  separated  the  full  length  of  the  coil  and  the  voltage 
difference  between  the  successive  reels  or  pancakes  is  only  a  fraction  of 
the  total  voltage. 

The  secondary  winding  of  a  coil  should  also  be  well  insulated  from 
the  primary  winding.  For  insulating  purposes  a  material  having  a  high 
dielectric  or  insulating  strength  should  be  used.  The  best  dielectric  ma- 
terials are  glass,  mica,  rubber,  paraffined  paper,  "  empire  cloth,"  porce- 
lain, etc.  For  this  particular  purpose,  empire  cloth  is  particularly  suited, 
having  a  high  dielectric  strength  and  being  flexible  and  comparatively 
thin. 

53.  Coil  Impregnation.  —  Induction  coils  are  sometimes  treated  by  a 
special  process  in  which  an  attempt  is  made  to  exclude  all  moisture.  If 
any  moisture  remains,  the  coils  will  always  cause  more  or  less  trouble, 
due  to  short  circuits  and  consequent  breaking  down  of  the  insulation. 
The  usual  practice  consists  of  placing  the  coils  in  a  large  steam  jacketed 
tank,  sealed  absolutely  air-tight,  and  heated  for  6  hours  to  a  tempera- 
ture of  250°F.  This  temperature,  being  above  the  boiling  point  of 
water,  drives  the  moisture  out  of  the  windings.  At  the  end  of  this  period 
a  vacuum  is  created  in  the  tank,  drawing  out  all  the  moisture,  after 
which  a  molten  dielectric  solution  such  as  wax  or  paraffin  is  allowed  to 
flow  in.  A  pressure  of  125  Ib.  to  the  sq.  in.  is  then  maintained  for  about 
3  hours  in  the  tank  containing  the  coils.  This  pressure  forces  the 
dielectric  or  insulating  compound  into  every  pore  of  the  paper  and  silk 


56  AUTOMOTIVE  IGNITION  SYSTEMS 

insulation,  replacing  the  moisture  that  has  been  removed  by  the  high 
temperature  and  vacuum  process. 

54.  Operation  of  the  Simple  Jump-spark  Ignition  System. — In  Fig. 
72  is  shown  a  circuit  diagram  of  a  simple  ignition  system  for  a  single 
cylinder  four-cycle  engine.  The  induction  coil  is  of  the  non-vibrating 
type  operating  with  a  breaker  for  making  and  breaking  the  primary  cur- 
rent. It  will  be  noticed  that  a  condenser  is  connected  across  the  breaker 
contact  points.  This  is  to  protect  the  points  against  pitting  and  to  assist 
the  primary  coil  in  inducing  a  high  voltage  in  the  secondary  winding. 
(The  operation  of  the  condenser  is  taken  up  in  Section  55.)  The  breaker 
points  are  normally  held  closed  by  spring  tension  and  open  only  when  the 
lobe  of  the  cam  lifts  the  movable  contact  arm.  This  cam  is  driven  by 
the  engine  and  rotates  at  one-half  crankshaft  speed  in  order  to  produce 
one  spark  in  two  revolutions  of  the  crankshaft.  The  cam  must  be  timed 
with  the  engine  so  that  the  spark  will  occur  when  the  piston  is  nearing 
the  end  of  its  compression  stroke. 

When  the  switch  is  turned  to  the  "ON"  position,  and  the  cam  is  in 
such  a  position  that  the  breaker  contacts  are  closed,  current  flows  through 
the  primary  circuit  from  the  positive  (+)  terminal  of  the  dry  cells, 
through  the  switch  and  primary  winding  of  the  coil  (magnetizing  the 
core  as  indicated),  to  the  insulated  terminal  of  the  breaker.  From  here 
it  crosses  the  breaker  contacts  and  passes  through  the  contact  arm  to  the 
ground,  returning  through  the  ground  to  the  negative  (  — )  grounded 
terminal  of  the  dry  cells,  thus  completing  the  circuit.  (A  ground  circuit 
is  that  part  of  the  circuit  in  which  the  current  travels  through  the  engine 
and  chassis  frame,  the  frame  or  ground  acting  as  a  conductor  the  same 
as  one  wire.)  When  the  primary  current  is  interrupted  by  the  cam  lobe 
lifting  the  breaker  contact  arm  so  that  the  contact  points  are  separated, 
the  core  demagnetizes  thus  causing  the  magnetic  lines  of  force  to  collapse 
toward  the  core,  cutting  each  turn  of  the  primary  and  secondary  winding. 
This  sudden  collapse  of  the  magnetic  lines  induces  a  current  in  both  wind- 
ings causing  it  to  flow  around  the  core  in  the  same  direction  as  the  original 
battery  current.  By  having  several  thousand  turns  of  very  fine  wire  in 
the  secondary  winding,  sufficiently  high  voltage  will  be  induced  in  the 
secondary  circuit  to  force  a  current  to  jump  across  the  spark  plug  points, 
thus  completing  the  circuit  and  giving  the  desired  ignition  spark  within 
the  cylinder.  The  path  followed  by  the  secondary  current,  as  shown  by 
the  arrows,  leads  from  one  end  of  the  secondary  winding  to  the  spark  plug 
terminal,  through  the  insulated  electrode  of  the  plug,  jumping  the  gap 
between  the  plug  points  to  the  engine  frame,  and  returning  through  the 
engine  frame  to  the  other  end  of  the  secondary  winding.  It  will  be  seen 
that  the  primary  winding  and  its  current  are  used  for  magnetizing  the 
core,  while  the  current  which  is  induced  in  the  secondary  coil,  when  the 
primary  circuit  is  broken,  is  that  used  for  the  ignition  spark. 


THE  JUMP-SPARK  IGNITION  SYSTEM 


57 


A  voltage  will  be  induced  in  the  secondary  winding  when  the  core 
is  being  magnetized  as  well  as  when  it  is  being  demagnetized,  but  owing 
to  the  fact  that  the  core  magnetizes  more  slowly  than  it  demagnetizes, 
the  induced  voltage  at  this  time  is  negligible.  When  the  primary 
circuit  is  broken,  the  core,  assisted  by  condenser  action,  demagnetizes 
very  rapidly  and  induces  a  current  of  very  high  voltage  in  the  secondary 
winding. 

55.  The  Condenser. — The  action  of  the  primary  circuit  is  very 
similar  to  that  of  the  kick  coil  in  a  make-and-break  ignition  system, 
and  the  same  kind  of  a  flashy  spark  which  occurs  between  the  igniter 
points  also  occurs  at  the  interrupter  points  when  the  primary  circuit 


INDUCTION  COIL 

IV 

/>5v> 


ECONDARY 
WINDING 


DATTERY 


^    HIGH  TENSION 
SPARK 


PRIMARY  WINDING 


CONTACT  POINTS 
"/HELD  NORMALLY  CLOSED^ 
\THROUQM  SPRING  TENSION/ 


CONDENSER 

FIG.  73. — Operation  of  the  condenser. 

is  broken.  In  the  jump-spark  ignition  system  this  spark  is  prevented 
and  the  action  of  the  coil  greatly  improved  by  the  use  of  a  condenser. 
The  condenser  usually  consists  of  two  folded  strips  of  tinfoil  in- 
sulated from  each  other  by  other  strips  of  paraffined  paper,  each  strip 
of  tinfoil  being  provided  with  a  terminal.  The  condenser  may  also 
be  made  up  of  small  sheets  of  tinfoil  insulated  by  thin  sheets  of  mica 
of  approximately  .002  in.  to  .003  in.  in  thickness.  With  this  con- 
struction, the  alternate  sheets  of  tinfoil  are  connected  in  parallel,  thus 
forming  two  groups,  the  sheets  in  each  group  being  connected  (usually 
soldered)  along  the  edge,  forming  in  all  two  common  terminals  for  ex- 
ternal connection.  The  two  condenser  terminals  are  connected  to 
the  interrupter  terminals  as  shown  in  the  circuit  diagrams  of  Fig.  72 
and  Fig.  73.  The  condenser  may  be  mounted  either  in  the  breaker 


58 


AUTOMOTIVE  IGNITION  SYSTEMS 


head  or  in  the  coil  housing,  preferably  as  near  to  the  breaker  points 
as  possible.  In  either  case,  the  condenser  should  be  well  protected 
against  moisture  or  physical  damage.  There  is  no  electric  circuit  through 
a  good  condenser.  If,  under  operating  conditions,  current  does  pass 
through  the  condenser  it  is  short  circuited  and  must  be  replaced.  The 
condenser  has  the  property  of  being  able  to  absorb  and  discharge  an 
electric  charge,  and  it  is  this  characteristic  which  makes  its  use  es- 
sential to  jump-spark  ignition. 

Referring  to  Fig.  73,  the  operation  of  the  condenser  is  as  follows: 
When  the  break  of  the  primary  circuit  occurs,  the  induced  surge  of 
current  in  the  primary,  which  is  in  the  same  direction  as  the  original 
battery  current  and  which  would  otherwise  cause  an  arcing  between 
the  contact  points,  rushes  into  the  condenser  and  charges  it.  The 

side  of  the  condenser  which 
receives  the  surge  is  tem- 
porarily charged  positive  and 
the  other  side  negative.  In- 
stantly, the  condenser  dis- 
charges back  through  the 
primary  winding  and  battery 
in  the  opposite  direction  in  an 
attempt  to  equalize  the  poten- 
tial of  the  two  sides.  As  this 
backward  surge  is  opposite  in 
direction  to  the  original  mag- 
netizing current,  it  assists  in 
quickly  reducing  the  mag- 
netism of  the  core  to  zero, 
thus  aiding  in  securing  the 
maximum  voltage  in  the  sec- 
ondary winding.  In  reality,  the  current  surges  or  oscillates  to  and 
fro  from  the  condenser  before  it  finally  dies  out.  The  initial  conden- 
ser discharge  is  represented  by  the  crooked  arrows  in  Fig.  73. 

The  action  of  the  condenser  may  be  compared  to  that  of  the  flex- 
ible diaphragm  shown  in  Fig.  74.  When  the  valve  is  closed,  suddenly 
cutting  off  the  flow  of  water  from  tank  B  through  the  coil  of  pipe 
into  tank  A,  the  water  depresses  the  diaphragm  for  an  instant,  due 
to  the  momentum  attained  by  the  water.  The  diaphragm  will  then 
rebound  immediately,  forcing  a  surge  of  water  back  through  the  pipe 
into  B;  in  fact,  the  water  will  surge  back  and  forth  several  times  before 
it  finally  comes  to  a  standstill  in  the  pipe.  This  surging  action  of 
the  water  may  be  compared  to  the  surging  of  the  electric  current  upon 
successive  discharges  of  the  condenser. 

Since  the  condenser  is  subjected  to  the  full  kick  voltage  of  the  coil, 


PIPE  COIL. 


FLEXIBLE  DIAPHRAGM 

FIG.     74. — Water    analogy    explaining    action    of 
condenser. 


THE  JUMP-SPARK  IGNITION  SYSTEM  59 

namely,  150  to  300  volts  impressed  across  the  contact  points  at  the 
instant  the  primary  current  is  interrupted,  it  is  evident  that  a  good 
insulating  material  between  the  tinfoil  plates  is  essential  in  order  that 
no  connection  between  the  opposite  plates  may  occur  through  a  punc- 
turing of  this  material.  If  a  flashy  spark  occurs  at  the  interrupter 
points,  it  is  usually  self-evident  that  the  condenser  has  become  either 
broken  down  (short  circuited)  or  disconnected. 

The  capacity  of  a  condenser  depends  on  the  size,  number,  and  ar- 
rangement of  the  tinfoil  plates,  and  upon  the  thickness  and  quality 
of  the  dielectric  material  between  them.  The  actual  number  of  square 
inches  of  tinfoil  needed  in  a  condenser  depends  upon  the  size  of  the 
wire  and  the  number  of  turns  in  the  coil  windings;  the  shape  and  quality 
of  the  iron  core;  and  upon  the  speed  of  the  interrupter.  Condenser 
capacity  is  usually  determined  experimentally  and  that  capacity  used 
which  gives  the  most  satisfactory  ignition.  The  action  of  a  good  con- 
denser of  proper  capacity  results  in  intensifying  the  secondary  cur- 
rent nearly  25  times.  It  also  eliminates  any  arcing  at  the  breaker 
points,  when  they  are  separated,  thus  preventing  rapid  pitting  and 
wearing  away  at  the  contact  points. 

56.  The  Safety  Gap. — Owing  to  the  extremely  high  voltage  induced 
in  the  secondary  winding  of  an  induction  coil  upon  the  interruption  of 
the  primary  circuit,  a  gap  of  %6  m-  to  %  in.  known  as  a  safety  gap  is 
usually  provided  across  the  ends  of  the  secondary  winding,  in  parallel 
with  the  gaps  of  the  spark  plug  points.     The  purpose  of  this  is  to  provide 
a  by-pass  for  the  high- voltage  current  in  case  a  spark  plug  lead  should  be- 
come disconnected  thus  causing  the  secondary  circuit  to  be  opened,  or,  in 
case  the  spark  plug  points  should  become  too  far  apart  for  the  spark  to 
jump  when  subjected  to  the  high  compression  of  the  gas  in  the  cylinder. 
In  case  such  a  breaker  extra  high  resistance  should  occur  in  the  secondary 
circuit,  which  offers  greater  resistance  to  the  high-tension  current  than 
the  resistance  across  the  safety  gap,  the  spark  will  jump  the  safety  gap, 
thereby  safeguarding  the  winding  of  the  coil  against  any  excessive  voltage 
which  might  puncture  the  insulation  and  cause  short  circuits. 

57.  Spark  Plugs. — Figure  75  illustrates  the  internal  construction  of 
several  typical  spark  plugs.     The  center  terminal  is  insulated  from  the 
rest  of  the  plug  and  the  other  terminal.     The  insulation  between  the 
center  electrode  and  the  body  of  the  plug  is  usually  either  of  porcelain  or 
of  mica.     The  outside  terminal  is  in  contact  with  the  engine  cylinder  and 
is,  consequently,  grounded.     The  only  way  the  current  can  get  from  one 
terminal  to  the  other  is  across  the  air  gap  between  them.     The  proper 
gap  between  the  points  for  ignition  systems  used  on  automobile  engines 
of  normal   compressions  up  to  80  Ib.  should  usually  be  about  ^2  in. 
(.030  in.)  or  the  thickness  of  a  worn  dime.     This  adjustment,  however, 
may  vary  slightly  with  the  type  of  ignition  equipment  used. 


60 


AUTOMOTIVE  IGNITION  SYSTEMS 


Some  plugs  are  made  with  a  single  grounded  electrode;  others  are 
made  with  two  or  more.  Certain  advantages  are  claimed  for  multiple- 
pointed  plugs,  chief  of  which  is  a  surer  spark.  In  time,  the  gap  gradually 
widens,  due  to  a  burning  of  the  points.  Consequently,  a  single-point 
plug  will  need  adjustment  of  the  gap  from  time  to  time.  In  the  case  of 
plugs  with  several  grounded  points,  it  is  claimed  the  electrodes  will  not 
burn  up  so  fast,  and,  therefore,  will  require  less  attention. 

A  good  serviceable  plug  will  not  short  circuit,  leak,  or  break  down. 
Short  circuiting  is  usually  caused  by  a  deposit  of  carbon  on  the  porcelain 
or  mica  elements.  This  may  be  caused  either  by  too  rich  a  mixture,  or  by 
too  much  lubricating  oil,  or  both.  Good  spark  plugs  are  assembled  so  as 
to  be  gas-tight.  This  necessitates  using  good  copper  or  asbestos  gaskets  of 
durable  construction  since  it  becomes  necessary  to  disassemble  the  plugs 
from  time  to  time  for  the  purpose  of  removing  carbon  deposits.  The 


BINDING     POSTS 
-TO  INSULATED    ELECTRODES 


CONICAL.  TTPE 

INSULATOR 
HELD  IN  PLACE 

BY      BUSHING 


BOSCH     PLUS 

SHOWING   INSULATOR 
SEALED    IN    POSITION 


FIG.  75. — Sections  of  typical  spark  plugs. 

insulation  must  be  of  high-quality  material  to  confine  the  electric  current 
to  the  insulated  electrode;  in  fact,  any  current  leakage  through  the 
procelain  or  mica  renders  the  spark  plug  practically  worthless.  Figure 
76  shows  a  few  of  the  many  types  of  spark  plugs  now  in  use.  Although 
the  designs  vary  somewhat  to  suit  varying  conditions  of  service,  the  re- 
quirements mentioned  above  are  fulfilled  in  each  type. 

In  automobile  and  aviation  engines  of  moderate  compression,  the 
voltage  required  to  jump  the  gap  of  the  spark  plug  points,  when  properly 
adjusted,  is  approximately  6,000  volts.  This  " break  down"  voltage, 
however,  may  vary  a  great  deal,  depending  upon  the  density  of  the  com- 
pressed gas,  since  the  voltage  increases  or  decreases  in  proportion  to  the 
increase  or  decrease  of  the  gas  density.  The  gas  density  in  turn  depends 
upon  the  compression,  the  proportion  of  gasoline  and  air,  and  the  tem- 
perature of  the  compressed  mixture.  Thus  it  will  be  seen  that  in  engines 


THE  JUMP-SPARK  IGNITION  SYSTEM 


61 


of  high  compression  the  spark  plug  points  should  be  adjusted  a  trifle  closer 
than  in  engines  of  low  compression  in  order  to  compensate  for  the  in- 
creased resistance  of  the  gas  when  subjected  to  the  higher  pressure  and  in 
order  to  insure  a  good  ignition  spark.  Common  practice  is  to  set  the 


BUSHING 


PORCELAIN 
INSULATOR 
x 


CHAMPION      STERLING 


OUTER 
SHELL 


V-RAY 


MONARCH       HERCULES       NATIONAL 


FIG.  76. — Types  of  spark  plugs. 

spark  plug  points  to  a  gap  of  .025  in.  to  .030  in.  for  automobile  engines 
with  compressions  less  than  80  lb.,  and  .020  in.  for  aviation  engines  with 
compressions  up  to  125  lb. 

One  of  the  important  factors  in  the  successful  operation  of  a  spark  plug 


62 


AUTOMOTIVE  IGNITION  SYSTEMS 


is  its  proper  installation  in  the  cylinder  or  cylinder  head.  The  location 
of  the  spark  plug  in  the  cylinder  head  is  governed  largely  by  the 
type  of  head  used.  The  usual  spark  plug  locations  in  the  I-head,  L- 
head,  and  T-head  types  of  engines  are  shown  in  Fig.  77.  This  figure 
also  shows  the  typical  arrangement  of  the  valves  and  the  shape  of  the 
combustion  chamber  for  each  type  of  engine,  both  of  which  have  consider- 


I-head  L-head  T-head 

FIG.  77. — Arrangement  of  valves  and  spark  plugs  in  various  types  of  engines. 

able  influence  on  ignition.  Since  the  cylinder  head  construction  varies 
in  thickness  on  the  different  types  of  engines,  the  spark  plug  shells  are 
made  in  several  different  lengths  so  as  to  locate  the  sparking  points  in 
proper  relation  to  the  gases  in  the  combustion  chamber.  The  shell 
should  be  of  such  length  that  when  the  plug  is  screwed  into  place  the 
inner  edge  of  the  shell  comes  flush  with  the  inside  of  the  cylinder  head  wall 


CORRECT  INCORRECT 

FIG.  78. — Correct  and  incorrect  methods  of  installing  spark  plugs. 

as  shown  in  Fig.  78.  If  the  shell  extends  beyond  the  inner  surface  of  the 
cylinder,  there  is  danger  of  the  plug  overheating,  thus  causing  premature 
ignition.  On  the  other  hand,  if  the  plug  does  not  extend  entirely  through 
the  hole  into  which  it  screws,  a  pocket  is  formed  for  the  burned  dead  gases, 
and  there  is  danger  of  misfiring,  owing  to  the  difficulty  of  the  fresh  gases 
in  reaching  the  spark  plug  points.  There  is  also  danger  of  the  plug 
fouling  badly  (short  circuiting)  by  oil  or  carbon  accumulation. 


THE  JUMP-SPARK  IGNITION  SYSTEM 


63 


In  order  that  the  spark  plugs  used  by  different  engine  manufacturers 
may  be  made  interchangeable,  as  far  as  possible,  the  dimensions  of  the 
shell  portion  have  been  standardized  to  conform  to  the  dimensions  shown 
in  Fig.  79  as  recommended  by  the  Society  of  Automotive  Engineers.  The 
threaded  portion  is  %in.  in  diameter  and  has  a  pitch  of  18  threads  per  in. 
This  is  known  as  the  S.  A.  E.  standard.  This  size  of  plug  has  been 
adopted  as  standard  on  practically  all  present  American  makes  of  auto- 
mobiles with  the  exception  of  three  or  four  makes  which  use  either  the 
%  in.  diameter,  18  thread  shell,  or  the  %  in.  size  having  standard  pipe 
threads.  The  latter  size  is  standard  for  the  Ford  car. 


SMALL  H£X  £  ACROSS  FLAT5.     LARGE  HEX.  l§  "ACROSS  FLATS. 


FIG.  79. — Spark  plug  shell  dimensions. 

The  upper  part  of  the  spark  plug  shell  is  made  in  two  sizes,  as  may 
be  seen  from  Fig.  79,  while  the  dimensions  below  the  shoulder  are  identi- 
cal for  both  sizes  of  shells.  With  these  dimensions  the  spark  plugs  can 
be  turned  in  by  hand,  using  a  wrench  only  for  final  tightening.  The 
thread  taps  used  should  be  made  to  dimensions  as  follows : 


Diameters 

Nominal 
Dimension 

Thread  Limits 

Spark  Plug 

Tap 

Outside  (A)  

0.875 

0.872  Min. 
0.875  Max. 

0.877  Min. 
0.879  Max. 

Pitch  (B)  

0.839 

0.836  Min. 
0.839  Max. 

0.841  Min. 
0.843  Max. 

Root  (C)  

0.803 

0.800  Min. 
0.803  Max. 

0.805  Min. 
0.807  Max. 

64 


AUTOMOTIVE  IGNITION  SYSTEMS 


The  nominal  tap-drill  diameter  is  I^{Q  in.  or  0.8125  in.;  the  minimum 
diameter  is  0.810  in.  and  the  maximum  0.813  in. 

Spark  Plug  Terminal  Threads. — The  standard  thread  used  for  spark 
plug  terminals  is  No.  8-32  (0.164  in.  dia.)  A.  S.  M.  E.  standard.  , 

58.  The  Vibrating  Induction  Coil. — The  vibrating  coil  ignition  system 
differs  from  the  non-vibrating  type  chiefly  in  the  addition  of  a  vibrator 
for  the  coil  and  the  employment  of  a  timer  instead  of  a  breaker  for  opening 
and  closing  the  primary  circuit.  The  essential  parts  of  the  coil  are  a 
core  of  soft  iron  wire;  a  primary  winding  of  coarse  insulated  wire";  a 
secondary  winding  of  fine  insulated  copper  wire;  a  condenser;  and  a 
vibrator. 

CONDENSER 


-    5PARK  PLUO 


SOFT  IRON  CORE 
(COMPOSED  OF  PUNDUE  or 

SOFT  IRON    WIRES  ) 


-TIMER 


GROUND*THROUGM'e.NGiNF  AND  CAP  FRAME 

FIG.  80. — Simple  jump-spark  ignition  system  with  vibrating  coil  and  timer. 


In  Fig.  80  is  shown  a  circuit  diagram  of  a  simple  jump-spark  ignition 
system  using  a  vibrating  coil  with  timer.  There  are  two  separate  and 
distinct  electric  circuits,  namely,  the  primary  circuit,  and  the  secondary 
circuit  the  same  as  in  the  non-vibrating  system.  The  primary  or  battery 
circuit  includes  the  battery,  the  switch,  the  vibrator,  the  primary  winding 
of  the  coil,  the  timer,  and  the  condenser.  The  condenser  is  connected 
across  the  vibrator  points.  The  secondary  circuit  contains  the  fine  or 
secondary  winding  of  the  coil  and  the  spark  plug.  When  the  primary 
circuit  is  completed  at  the  timer  (which  is  usually  driven  by  the  camshaft 
of  the 'engine),  current  will  flow  from  the  battery  through  the  primary 
winding  of  the  coil  in  the  direction  indicated  by  the  arrows.  The  core  of 
the  coil  thus  becomes  magnetized  and  as  long  as  the  current  flows  this 
core  will  have  the  properties  of  a  magnet.  The  core  exerts  a  pull  on  the 


THE  JUMP-SPARK  IGNITION  SYSTEM 


65 


VIBRATOR   POINTS 
CONTACT  SPRING 


iron  disc  or  armature  attached  to  the  end  of  the  vibrator  and  in  so  doing 
separates  the  contact  points  on  the  vibrator  from  the  stationary  contact. 
This  breaks  the  primary  circuit  and  the  current  ceases  to  flow.  The 
core  then  loses  its  magnetism  and  the  vibrator  returns  to  its  former  posi- 
tion. In  so  doing,  it  reestablishes  the  primary  circuit  and  the  action  is 
repeated.  Thus,  as  long  as  the  primary  circuit  is  closed  by  the  roller 
making  contact  with  the  segment  of  the  timer,  the  vibrator  will  vibrate 
rapidly,  similar  to  the  vibrator  of  an  ordinary  electric  doorbell. 

Each  time  the  vibrator  opens,  breaking  the  primary  circuit,  the 
magnetic  field  dies  away  very  quickly  followed  by  a  high-tension  spark 
at  the  plug.  The  flashy  spark  which  would  naturally  occur  at  the  vibra- 
tor points  is  absorbed  by  the  condenser  which  is  connected  across  the 
points.  Since  the  vibrator  makes  and  breaks  many  times  during  each 
contact  of  the  timer,  a  shower 
of  sparks  is  delivered  at  the 
plug.  These  sparks  begin  at 
the  instant  the  timer  contact 
is  made  and  last  throughout 
the  period  of  contact. 

59.  The     Three-terminal 
Coil. — Many  of  the  coils  used 
on  automobile  ignition 
systems    have    only    three 
terminals  instead  of  four.     In 
Fig.   81    is   shown   a   typical 
three-terminal  coil  such  as  is 
used  on  the  Ford  car.     One 
end  of  the  secondary  winding 
is  joined  to  one  end  of  the 
primary,    and    the     junction 

connected  to  one  of  the  terminal  binding  posts  which,  when  connected  in 
the  system,  leads  to  the  ground  through  the  primary  wiring.  The  other 
end  of  the  secondary  has  a  separate  terminal  which  is  connected  to  the 
spark  plug. 

60.  The  Vibrating  Type  Ignition  System. — Where  vibrating  coils  are 
used  for  ignition  on  a  multiple  cylinder  engine,  it  is  customary  to  use  a 
coil  for  each  cylinder.     These  coils  are  usually  enclosed  in  an  upright  box. 
as  shown  in  Fig.  82,  which  is  a  coil-set  for  a  four-cylinder  engine.     The 
box  is  fitted  with  interchangeable  slip-type  coil  units  such  as  that  in  Fig. 
81.     The  connections  for  these  coils  are  made  by  contact  springs  in  the 
coil  box  bearing  on  the  metal  contacts  of  the  coil  as  shown  in  Fig.  83. 
This  makes  it  possible  to  remove  any  of  the  coils  without  disconnecting 
any  of  the  wiring.     The  switch  on  the  front  of  the  box  permits  the  prim- 
ary current  to  be  used  from  either  a  battery  or  low-tension  magneto. 


FIG.  81. — Ford    induction    coil,    showing 
three-terminal  coil. 


VIBRATOR 
ADJUSTING 


PRIMARY 

WINDING 


£\l  _  PR'M 

I  /  ""  -  TERMINAL 

n  CONTACT 

SECONDARY 
WINDING 


SECONDARY 

TERMINAL 

CONTACT 

SOFT  IRON 

CORE 
\PRIMARY    TERMINAL  CONTACT 

typical 


66 


AUTOMOTIVE  IGNITION  SYSTEMS 


This  system  may  also  be  used  with  two  independent  batteries,  one  being 

held  in  reserve. 

Figure  83  shows  the  circuit  diagram  of  a  typical  vibrating  coil  ignition 

system  for  a  four-cylinder  engine  using 
either  dry  batteries  or  low-tension  mag- 
neto as  the  source  of  current  supply. 
This  is  similar  to  the  Ford  system  of 
ignition  which  is  taken  up  in  detail  in 
Chapter  VI. 

61.  Timers. — The  timer  may  be 
denned  as  a  revolving  switch  driven 
by  the  engine  for  the  purpose  of  con- 
necting the  source  of  primary  current 
supply  to  the  proper  vibrating  induc- 
tion coil  at  the  proper  time.  It  is, 

FIG.  82.-Ford  four-cylinder  coil-set.     conse<iuently,    always    placed    in    the 

primary  circuit.     The   timer  used    on 

the  Ford  engine  is  shown  in  Fig.  84.     The  inside  or  rotating  part  is 
fastened  to,  and  rotates  with,  the  camshaft  at  one-half  crankshaft  speed. 


CONTACT  PLATE  IN  BASE/ 
OF   COIL  BOX-— -^, 


MAGNETO 

TERMINAL 


_ __  _ J3RO.U N D —  _ -€ 


(ONE  SIDE  OF  MAGNETO 
WINDING    GROUNDED) 


FIG,  83. — Diagram  of  four-cylinder  vibrating  coil  ignition  system. 

When  the  roller  comes  into  contact  with  one  of  the  four  terminals  on  the 
timer  housing,  the  primary  circuit  is  completed  through  the  coil  which  is 
connected  to  that  terminal,  causing  its  vibrator  to  operate  and  a  series  of 


THE  JUMP-SPARK  IGNITION  SYSTEM 


67 


sparks  to  occur  in  rapid  succession  at  the  plug.  The  housing  of  the 
timer  does  not  turn  with  the  camshaft,  but  can  be  shifted  forward  or 
backward  in  respect  to  the  camshaft  and  roller  so  as  to  advance  or  retard 
the  time  of  the  spark. 


Pull  Rod  Connection 

Case 

Thumb  Nut 

Contact  Point 

'- Roller  Arm 

Brush 

Engine  Cover 


FIG.  84. — The  Ford  timer. 

The  timers,  when  used  for  six-,  eight-,  and  twelve-cylinder  engines, 
are  similar  to  the  above  but  instead  of  four  terminals,  have  six,  eight,  or 
twelve  insulated  terminals  equally  spaced  in  the  housing. 

62.  Master  Vibrators. — A  master  vibrator  is  a  single  vibrator  or 
interrupter  that  takes  the  place  of  the  separate  vibrators  of  the  coil 
units  on  a  multi-cylinder  engine,  doing 
away  with  the  separate  vibrator  ad- 
justment for  the  different  coils.  With 
this  system  one  fast  vibrator  with  a 
good  condenser  will  produce  sparks  of 
like  intensity  at  each  of  the  plugs. 
Figure  85  shows  the  external  view  of  a 
K-W  master  vibrator  with  a  three-posi- 
tion switch  which  permits  the  use  of  a 
low-tension  magneto  or  a  battery  to 
furnish  the  current  for  ignition.  A 
master  vibrator  is  quite  similar  in  con- 
struction to  a  vibrating  coil  except  that 
it  has  no  secondary  winding.  It  consists 
of  an  iron  core,  a  switch,  and  a  vibrator 
across  the  points  of  which  a  condenser  is 
connected.  The  master  vibrator  is  con- 
nected in  series  with  the  batteries  and  the  coils  so  that  the  primary 
current  passes  through  the  master  vibrator  coil  before  going  to  the  in- 
duction coils.  The  master  vibrator  thus  operates  regardless  of  which 
cylinder  is  firing.  Figure  86  shows  the  Pfanstiehl  master  vibrator,  which 
is  cylindrical  in  shape. 


FIG.  85. — K-W  master  vibrator. 


68 


AUTOMOTIVE  IGNITION  SYSTEMS 


When  a  master  vibrator  is  installed  in  connection  with  coils  hav- 
ing separate  vibrators,  a  change  is  made  in  the 
coils,  cutting  out  or  short  circuiting  the  separate 
condenser  and  vibrators.  This  may  be  done  by 
simply  screwing  down  each  of  the  vibrator  con- 
tacts so  that  they  make  firm  contact  and  cannot 
vibrate.  The  three-position  switch  on  the  coil 
box  is  also  discontinued  and  that  on  the  master 
vibrator  used  instead.  Figure  87  shows  a  wiring 
diagram  for  a  four-cylinder  coil-set  with  a  master 
vibrator  such  as  is  often  equipped  on  the  Ford 
car.  This  diagram  shows  the  switch  thrown  to 
"  Magneto "  position  so  that  the  magneto  is 
furnishing  the  primary  current.  The  firing  order 
is  1,  2,  4,  3,  and  the  connection  is  shown  to  give 
a  spark  in  cylinder  No.  1. 

The  demand  for  such  a  device  as  a  master 
vibrator  has  been  brought  about  by  the  difficulty 
experienced  in  securing  uniform  adjustment  of  the  various  vibrators,  by 


FIG.  86.— Pf anstiehl  tubular 
type  master  vibrator. 


VIBRATOR 


CONDENSER 


FIG.  87.  —  Wiring  ^diagram    of    four-cylinder    ignition    system   using    master  vibrator   in 
connection  with  four  vibrating  type  coils. 

deterioration  of  the  vibrator  points,  and  by  the  frequent  troubles  encoun- 
tered with  defective  condensers,  it  being  about  as  cheap  to  install  a 


THE  JUMP-SPARK  IGNITION  SYSTEM  69 

master  vibrator  as  to  replace  the  expensive  points  or  to  buy  new  coils. 
As  the  condensers  and  vibrators  of  the  individual  coils  are  inoperative 
when  the  master  vibrator  is  used,  any  defects  in  those  parts  will  not 
prohibit  their  use  in  the  new  scheme.  One  advantage  in  using  a  master 
vibrator  is  due  to  the  fact  that  sparks  of  equal  intensity  are  delivered 
to  all  the  spark  plugs  as  the  result  of  one  vibrator  adjustment. 

63.  Spark   Advance   and   Retard. — On    a   variable    speed    gasoline 
engine  it  is  very  essential  that  the  time  at  which  the  spark  occurs  in 
the  cylinder  be  changed  according  to  the  engine  speed,  since -it  takes 
a  certain  length  of  time  for  the  explosion  to  take  place  regardless  of 
the  engine  speed.     When  the  engine  speed  is  high,   the  spark  must 
occur  before  the  piston  reaches  dead  center  in  order  to  have  the  full 
force  of  the  explosion  exerted  when  the  piston  has  just  passed  the  cen- 
ter position.     When  the  engine  speed  is  low,  the  spark  can  occur  later 
and  the  force  of  the  explosion  will  be  exerted  just  after  dead  center. 
It  is  necessary  when  starting  the  engine  that  the  spark  occur  when  a 
piston  is  approximately  on  dead  center;  but  when  the  engine  must 
start  on  ignition  from  a  high-tension  magneto,  the  spark  can    occur 
slightly  before  dead  center.     This  is  especially  true  when  an  electric 
starter  is  used  for  cranking,  since  the  engine  is  cranked  at  a  higher 
speed  and  with  sufficient  momentum  stored  in  the  flywheel   to   carry 
the  pistons  past  the  dead  center  positions. 

These  various  considerations  demand  that  the  position  of  the  spark 
be  made  variable.  This  is  usually  done  by  shifting  the  timer,  or  inter- 
rupter housing,  causing  the  break  of  the  primary  current  (and,  con- 
sequently, the  spark  in  the  cylinder)  to  occur  earlier  or  later.  The 
position  of  the  spark  in  most  cases  is  governed  by  the  spark  control 
lever  on  the  steering  wheel.  In  starting  the  engine,  the  spark  should 
be  retarded  so  that  ij^will  not  occur  until  the  piston  is  starting  on  its 
downward  stroke.  The  spark  should  then  be  advanced  as  the  engine 
increases  its  speed.  If  the  spark  is  too  far  advanced,  there  will  be  a 
decided  knock  in  the  cylinders.  The  best  results  are  obtained  with 
the  ignition  advanced  as  far  as  possible  without  causing  the  engine  to 
pound. 

64.  Principles  of  Ignition  Timing. — Correct  ignition  timing  is  one 
of  the  most  important  points  in  engine  economy.     The  best  efficiency 
will  be  obtained  when  the  time  of  ignition  is  so  regulated  that  the  great- 
er part  of  the  combustion  occurs  while  the  crank  is  passing  the  head 
or   upper    dead    center.     If  any  great  part  of  the  combustion  occurs 
before  the  dead  center  is  reached,  there  will  be  an  undue  pressure  ex- 
erted against  the  further  motion  of  the  piston  in  completing  the  com- 
pression stroke.     If  the  combustion  is  delayed,   the  full  fuel  energy 
will  not  be  available  for  the  whole  expansion  stroke  and  there  will  be 
a  consequent  loss  in  the  amount  of  work  secured  from  the  fuel. 


70 


AUTOMOTIVE  IGNITION  SYSTEMS 


The  rate  at  which  the  flame  spreads  through  the  fuel  mixture  de- 
pends on  the  quality  of  fuel  and  the  mixture.  A  weak  mixture  will 
burn  more  slowly  than  a  well-proportioned  one.  An  overly  rich  mixture 
will  also  burn  slowly.  A  fuel  low  in  heating  value  will  also  burn  more  slowly 
than  one  high  in  heat  units.  Fundamentally,  the  rate  of  flame  prop- 
agation through  the  charge  depends  upon  the  intensity  of  the  heat 
generated  by  the  combustion.  The  ignition  spark  starts  combustion 
in  a  small  sphere  surrounding  the  spark  plug  points.  The  heat  thus 
generated  is  transmitted  to  the  surrounding  charge,  which  in  turn 
burns  and  passes  the  heat  on  to  succeeding  layers.  The  rate  of  prop- 
agation thus  depends  on  the  intensity  of  the  heat  generated  in  each 
unit  of  volume  of  the  mixture.  Weak  gases  or  mixtures  must,  there- 
fore, mean  slower  combustion.  The  state  of  compression  also  affects 
the  rate  of  burning.  If  the  charge  is  compressed  into  a  smaller  space, 
the  intensity  of  the  heat  generated  in  each  unit  of  space  is  greater; 
the  flame  also  has  a  shorter  distance  to  travel  to  ignite  the  whole  charge. 


Double 
p/ug 


Distributor 


FIG.  88. — Series  plug  ignition  system. 

Thus  it  is  evident  that  the  shape  of  the  combustion  chamber  has 
considerable  influence  on  the  time  required  for  flame  propagation  and 
the  consequent  power  and  fuel  economy  of  the  engine.  In  this  respect 
the  I-  head  type  of  engine  has  the  advantage  over  the  L-  and  T-  head 
types,  Fig.  77,  since  it  has  the  most  compact  combustion  space  and, 
consequently,  the  shortest  distance  for  the  flame  to  travel. 

The  location  of  the  spark  plug  is  also  important  in  this  respect.  If 
it  is  located  near  the  center  of  the  combustion  chamber,  the  flame  will 
spread  through  the  whole  mass  more  quickly  than  if  ignition  occurs  at 
one  corner  of  the  combustion  chamber.  To  lessen  the  time  for  securing 
combustion,  T-head  engines  are  sometimes  provided  with  two  spark 
plugs  located  at  distant  points  in  the  cylinder  head,  usually  one  plug  over 
each  valve,  and  arranged  so  that  a  spark  will  occur  at  the  same  instant  in 
both  plugs.  This  arrangement  requires  the  use  of  one  special  plug, 
known  as  a  series  plug,  in  which  both  electrodes  are  insulated,  the  two 
plugs  being  connected  in  series  as  shown  in  Fig.  88. 


THE  JUMP-SPARK  IGNITION  SYSTEM  71 

It  will  be  evident  that  the  procedure  for  timing  the  ignition  apparatus 
with  the  engine  depends  largely  upon  the  type  of  ignition  system  used,  the 
characteristics  of  the  engine,  and  the  conditions  under  which  it  is  to 
operate.  Since  there  is  no  particular  gain  in  having  the  spark  occur 
much  after  the  piston  has  passed  the  upper  dead  center  position,  it  is 
usually  advisable  to  fix  the  time  of  the  spark  on  the  maximum  retard  in 
relation  to  the  engine  crankshaft,  rather  than  to  fix  the  time  of  the  spark 
for  maximum  advance.  This  will  give  the  operator  the  full  available  ad- 
vance range  through  which  he  may  advance  the  spark  ahead  of  dead  center, 
as  the  engine  speed  increases,  in  order  to  obtain  the  best  performance  of  the 
engine.  Thus  it  will  be  seen  that  the  chief  aim  in  ignition  timing  is  to 
fix  definitely  the  occurrence  of  the  spark  so  that  it  will  occur  in  the  cylin- 
der when  the  piston  is  approximately  on  upper  dead  center  position  at 
the  end  of  its  compression  stroke  with  the  ignition  breaker  or  timer  in 
full  retard  position.  It  should  be  remembered  that  in  ignition  systems 
using  a  non-vibrating  coil  and  breaker,  the  spark  occurs  at  the  plug  the 
instant  the  breaker  contact  points  separate;  while,  in  the  case  of  a  system 
using  vibrating  coils  with  a  timer,  a  shower  of  sparks  will  occur  at  the 
plug  the  instant  the  timer  contact  is  made.  The  exact  methods  employed 
in  ignition  timing  will  be  taken  up  later  in  connection  with  the  various 
types  of  ignition  systems. 


CHAPTER  IV 
MODERN  BATTERY  IGNITION  SYSTEMS 

65.  Construction  of  a  Typical  Battery  Ignition  System. — The  main 
parts  of  a  modern  automobile  battery  ignition  system  are:  a  storage 
battery,  a  high-tension  non-vibrating  induction  coil,  a  breaker,  and  a  dis- 
tributor. A  typical  installation  of  such  a  system  is  shown  in  Fig.  89. 
The  source  of  current  is  the  storage  battery,  which  also  supplies  current 
for  the  starting  and  lighting  system.  The  breaker  and  high-tension 
distributor  are  usually  combined  into  a  single  unit  driven  either  through 


.un.rATna  IGNITION  &  LIGHTING 

INDICATOR  '  _.    SWITCH 


— -\     I  STARTING  SWITCH 

_^  \AANDCUT-OUT 

TO  STARTER" 
GENERATOR 


"GROUND  IGNITION  UNIT 


FIG 


.  89. — Installation  and  wiring  of  North  East  ignition  system  on  Dodge. 


spiral  gears  on  one  end  of  the  generator  armature  shaft,  as  in  Fig.  90, 
or  by  a  separate  shaft  similar  to  the  method  of  driving  a  magneto  as 
shown  in  Fig.  89. 

The  induction  coil  is  usually  mounted  close  to  the  breaker  unit, 
common  locations  for  it  being  on  top  of  the  generator  as  in  Fig.  90;  on  a 
bracket  on  the  side  of  the  engine;  or  on  the  back  of  the  dash.  The  igni- 
tion switch  may  be  an  independent  switch;  or,  as  is  more  often  the  case, 
it  may  be  combined  with  the  lighting  switch.  This  switch  may  be 
mounted  either  on  the  instrument  board  or  on  the  steering  column  within 
convenient  reach  of  the  driver. 

A  wiring  diagram  of  a  typical  automobile  battery  ignition  system  for 
a  six-cylinder  engine  is  shown  in  Fig.  91.  As  may  be  seen,  the  breaker 
points  and  the  distributor  are  operated  by  a  single  vertical  shaft,  the 

73 


74 


AUTOMOTIVE  IGNITION  SYSTEMS 


distributor  arm  or  block  being  carried  on  the  upper  end  of  this  shaft  im- 
mediately above  the  cam  which  actuates  the  breaker  points. 


•     TERMINAL  CONNECTED 
TO  SWITCH 


IGNITION  COIL 


IGNITION 
DISTRIBUTOR 


THIRD  BRUSH 
SUPPORTING  PLATE- 


FIG.  90. — Delco  ignition  equipment  mounted  on  motor  generator  for  Buick  Six. 


IGNITION 
SWITCH 


AMMETER 


SPARK 
PLUG 


IGNITION  TIMER  SHAFT 

.(DRIVEN  AT  ONE-HALF 
CRANK  SHAFT  SPEED) 


GROUNDED    CIRCUIT  THROUGH    ENGINE  AND  FRAME 


FIG.  91. — Typical  battery  ignition  system. 


In  all  four-,  six-,  eight-,  or  twelve-cylinder  four-stroke  cycle  engines, 
such  as  used  in  automobiles,  trucks,  tractors,  and  airplanes,  all  of  the 


MODERN  BATTERY  IGNITION  SYSTEMS  75 

engine  cylinders  must  fire  in  two  revolutions  of  the  crankshaft.  This 
means  that  for  each  revolution  of  the  engine  crankshaft  one-half  of  the 
total  number  of  cylinders  must  fire  and  must  receive  an  ignition  spark. 
Thus  the  ignition  system  must  deliver  to  the  engine  cylinders  two  sparks 
for  a  four-cylinder  engine,  three  sparks  for  a  six-cylinder  engine,  four 
sparks  for  an  eight-cylinder  engine,  and  six  sparks  for  a  twelve-cylinder 
engine,  during  each  revolution  of  the  crankshaft. 

This  is  made  possible  by  using  a  four-,  six-,  eight-,  or  twelve-lobed 
cam  for  interrupting  the  primary  circuit,  and  a  high-tension  distributor 
with  as  many  equally  spaced  segments  as  there  are  cylinders  for  directing 
secondary  current  to  the  various  plugs  in  their  proper  order  of  firing. 
With  this  arrangement,  the  cam  and  distributor  are  both  driven  at  the 
same  speed,  namely,  one-half  that  of  the  crankshaft. 

Since  the  spark  occurs  in  the  cylinder  at  the  instant  the  breaker  points 
open,  it  is  very  essential  that  the  cam  lobes  be  ground  and  spaced  very 
accurately  so  that  the  spark  will  occur  in  each  cylinder  at  exactly  the 
same  point  in  the  revolution.  The  cam  lobes  and  distributor  segments 
are,  therefore,  spaced  to  correspond  to  the  angle  passed  through  by  the 
crankshaft  during  the  period  between  successive  cylinder  explosions. 
This  crank  angle  is  normally  180°  or  one-half  of  a  revolution  for  a  four- 
cylinder  engine,  120°  or  one-third  of  a  revolution  for  a  six-cylinder  engine, 
90°  or  one-fourth  of  a  revolution  for  an  eight-cylinder  engine,  and  60°  or 
one-sixth  of  a  revolution  for  a  twelve-cylinder  engine.  One  complete 
revolution  is  360°  so  that  the  angles  between  the  cams  may  be  readily  deter- 
mined by  dividing  720°  by  the  total  number  of  engine  cylinders.  For 
example:  the  crank  angle  between  explosions  in  a  six-cylinder  engine  is 
720°  -f-  6  or  120°.  Likewise,  in  a  twelve-cylinder  engine  this  angle  is 
720°  •*•  12  or  60°. 

66.  The  Breaker. — The  function  of  the  breaker  or  interrupter  is  to 
make  and  break  the  primary  circuit,  thereby  energizing  the  induction 
coil  and  producing  a  spark  at  the  plug  at  the  proper  time.  Where 
a  non-vibrating  coil  is  used,  the  secondary  spark  occurs  at  the  instant 
the  contact  points  open.  These  points  consist  of  two  small  contact  pieces, 
usually  tungsten  alloy  or  platinum,  one  of  which  is  stationary  while  the 
other  is  mounted  on  a  pivoted  arm  as  shown  in  Fig.  91.  This  arm  is  made 
to  bear  against  the  cam  by  spring  tension,  with  the  points  held  normally 
in  contact.  As  the  cam  revolves,  each  lobe  presses  against  the  contact 
arm  separating  the  points  about  .020  in.  The  opening  of  the  contact 
points  interrupts  the  current  in  the  primary  winding  of  the  coil  thus 
permitting  the  core  to  demagnetize  and  causing  a  high-voltage  current  to  be 
induced  in  the  secondary  winding.  The  points  being  made  of  tungsten 
alloy  or  platinum,  both  have  extremely  high  melting  points,  and  will 
withstand  burning  and  pitting  due  to  any  sparking  that  may  occur  when 
the  contacts  open.  To  prevent  this  sparking  as  much  as  possible,  a 
condenser  is  used,  it  being  electrically  connected  across  the  two  contacts. 


76  AUTOMOTIVE  IGNITION  SYSTEMS 

67.  The  Distributor. — As  previously  explained,  the  function  of  the 
distributor  is  to  direct  the  secondary  current  from  the  induction  coil  to 
the  various  spark  plugs  of  a  multi-cylinder  engine  in  the  proper  order  of 
operation.  The  distributor  head  or  cap  has  a  center  terminal  which 
connects  with  the  secondary  terminal  of  the  induction  coil,  and  as  many 
more  metal  segments  or  terminals  equally  spaced  around  it  as  there  are 
spark  plugs.  The  head  is  usually  molded  of  a  very  high  resistant  insulat- 
ing material  such  as  Bakelite  or  Condensite  which  is  moisture  proof  and 
possess  high  insulating  properties  even  under  excessive  heat.  The 
terminals  are  of  metal  alloy  molded  in  position  and  terminating  on  the 
underside  in  the  form  of  either  a  segment  flush  with  the  surface  of  the 
head,  or  in  the  form  of  a  pin  as  in  Fig.  91. 

The  center  terminal,  to  which  is  connected  the  high-tension  cable  from 
the  induction  coil,  has  a  button  or  brush  on  the  underside,  usually  of 
carbon,  which  makes  electrical  contact  with  the  center  point  of  the  spring 

or  segment  on  the  distributor  arm.  This  arm 
or  rotor,  which  is  usually  a  molded  block  of  the 
same  material  as  the  head,  fits  upon  the  shaft 
in  only  one  correct  position  relative  to  the 
cam,  so  that,  as  it  rotates,  its  distributing 
button  or  segment  always  comes  opposite  the 
correct  terminal  in  the  head  to  conduct  the 
spark  to  the  proper  cylinder  when  the  cam 
separates  the  breaker  points.  In  some  dis- 
tributors such  as  the  Delco,  North  East,  and 
Westinghouse  the  end  of  the  distributing  arm 
makes  rubbinS  contact  with  the  segments  in 
the  head  by  means  of  either  a  metal  button 
or  carbon  brush,  while  in  other  types  such  as  the  Remy,  Atwater-Kent, 
and  Connecticut,  the  outer  end  of  the  distributor  segment  merely  rotates 
close  to  the  terminal  extensions  without  quite  touching  them.  In  this 
type,  the  secondary  current  must  leap  the  small  gap  (usually  not  over  ^4 
in.)  between  the  segment  and  the  terminal  extension  in  order  to  complete 
its  current. 

The  distributor  head  is  usually  held  in  place  by  two  spring  clips 
which  fit  only  when  the  head  is  in  its  proper  position.  By  simply  remov- 
ing the  head,  the  distributing  arm  and  breaker  mechanism  are  readily 
accessible  for  inspection  and  adjustment.  On  systems  where  the  dis- 
tributor makes  a  wiping  contact,  it  is  advisable  to  remove  the  cap  about 
once  a  month,  or  each  1000  miles  of  travel,  and  wipe  the  track  clean, 
using  a  rag  slightly  moistened  with  vaseline  as  shown  in  Fig.  92.  This 
will  keep  the  distributor  track  polished  and  prevent  the  rotor  button 
from  sticking  and  cutting  the  track. 


MODERN  BATTERY  IGNITION  SYSTEMS.  77 

68.  The  Resistance  Unit. — The  resistance  unit,  Fig.  91,  which  is  very 
generally  used  on  automobile  storage  battery  ignition  systems,  plays  a 
very  important  part  in  the  operation  of  the  system  and  serves  as  a  pro- 
tective device  to  the  coil  and  battery  in  case  the  switch  is  left  "ON" 
with  the  engine  not  running. 

It  consists  usually  of  a  number  of  turns  of  resistance  wire  of  either 
German  Silver  or  a  special  Nickel-Chrome  alloy,  commonly  known  as 
"Nichrome, "  connected  in  the  primary  ignition  circuit.  The  important 
characteristic  of  this  wire  is  its  property  of  increasing  its  resistance  as 
it  is  heated  up,  the  change  in  resistance  being  used  to  control  the  current 
flowing  in  the  circuit.  For  this  purpose  "Nichrome"  wire  is  more  gen- 
erally used  since  its  increase  in  resistance  is  practically  in  direct  pro- 
portion to  its  increase  in  temperature  up  to  a  dull  cherry  red  heat 
(approximately  1400°F.),  which  temperature  may  be  considered  the 
highest  at  which  the  unit  will  operate  normally.  In  case  the  ignition 
switch  is  left  in  the  "ON"  position  with  the  engine  not  running  and  with 
the  breaker  closed,  the  resistance  wire  will  heat  up  immediately,  due  to 
the  current  flowing,  accompanied  by  a  sudden  rise  in  the  resistance. 
This  will  cause  the  current  discharge  from  the  battery  through  the  prim- 
ary winding  to  decrease  sufficiently  to  protect  the  coil  against  damage 
from  overheating  and  the  battery  against  rapid  discharge. 

69.  Effect  of  the  Resistance  Unit  upon  Ignition. — It  will  be  seen  that 
the  period  during  which  the  breaker  contact  points  remain  closed  at  high 
speed  is  exceedingly  brief,  while,  at  low  speed,  the  contacts  remain 
closed  for  comparatively  longer  periods  of  time.     This  causes  the  current 
consumption  to  be  slightly  greater  at  low  speeds.     In  order  to  limit  the 
increase  of  primary  current  to  an  amount  which  will  not  overheat  the 
coil,  the  resistance  unit  is  connected  in  the  primary  circuit  in  series  with 
the  coil  and  breaker,  it  being  usually  mounted  either  on  top  of  the  coil  or 
on  the  side  of  the  breaker  housing.     The  effect  of  a  slight  increase  of 
current  through  the  circuit  at  low  speeds  is  to  heat  up  this  resistance  unit, 
thus  increasing  its  resistance.     This  change  in  resistance  automatically 
decreases  the  current  at  the  lower  speeds  yet  permits  sufficient  current 
to  flow  through  the  coil  at  high  speeds  to  produce  an  effective  spark. 

It  will  also  be  seen  that  the  resistance  unit  tends  to  equalize  the  in- 
tensity of  the  secondary  spark  at  high  and  low  engine  speeds,  due  to  its 
change  in  resistance  and  the  difference  in  the  value  of  the  primary  cur- 
rent at  different  speeds.  The  period  of  time  which  the  primary  current 
has  for  magnetizing  the  core  will,  of  course,  decrease  in  proportion  to  the 
increase  in  engine  speed;  consequently,  since  it  requires  a  certain  length 
of  time  for  the  core  to  become  fully  magnetized  (usually  .001  to  .02  of  a 
second,  depending  upon  the  design  and  construction  of  the  coil),  there  is 
a  tendency  at  high  speed  for  the  breaker  to  interrupt  the  primary  current 
before  the  core  is  fully  magnetized,  thus  decreasing  the  intensity  of  the 


78 


AUTOMOTIVE  IGNITION  SYSTEMS 


secondary  spark.  This  is  counteracted,  to  a  certain  extent,  by  the  de- 
crease in  temperature  and  resistance  of  the  resistance  unit  at  high  speeds, 
as  a  decrease  in  resistance  will  permit  a  larger  momentary  flow  of  current 
through  the  primary  winding  during  the  brief  period  the  breaker  points 
are  closed.  By  thus  controlling  the  primary  current,  the  intensity  of  the 
secondary  voltage  is  kept  more  nearly  uniform  at  the  different  speeds 
of  the  engine. 

The  resistance  unit  also  assists  the  coil  to  produce  a  hotter  spark 
when  the  battery  voltage  is  low  since  at  that  time  the  current  is  cor- 
respondingly low,  and  the  temperature  and  resistance  of  the  unit  do  not 
increase  greatly. 

70.  Automatic  and  Manual  Spark  Advance. — In  several  modern 
automobile  ignition  systems,  means  are  provided  by  which  the  posi- 


AWUSTiNG  NUT 
CONTACT    POINTS 


DISTRIBUTOR 
CONTACT  BUTTON 


DISTRIBUTOR  ROTOR 
MOUNTED  ON    CAM 


AUTOMATIC   ADVANCE 
WEIGHTS 


AUTOMATIC  ADVANCE. 
RING 


MANUAL.  ADVANCE 
LEVER 


VIEW    or  BREAKER   MECHANISM 
WITH  DISTRIBUTOR  ROTOR  REMOVED 


VIEW   SHOWING  AUTOMATIC 
SPARK  ADVANCE  MECHANISM 


FIG.  93. — Delco  interrupter  and  automatic  spark  advance  mechanism. 


tion  of  the  spark  is  advanced  and  retarded  automatically  with  the  changes 
in  engine  speed.  The  purpose  of  this  is  to  relieve  the  driver  of  the 
responsibility  and  uncertainty  of  correctly  gaging  the  proper  position 
for/setting  the  spark  control  lever  during  normal  driving  speeds.  Figure 
93  shows  the  Delco  ignition  breaker  and  automatic  spark  advance 
mechanism  as  used  on  the  Hudson  Super-Six. 

As  can  be  seen  from  this  figure,  the  automatic  advance  mechanism 
is  in  the  form  of  a  revolving  weight  type  governor  mounted  on  the 
timer  shaft  below  the  interrupter  cam.  The  weights  are  carried  by 
a  ring  which  is  mounted  on  a  short  hollow  shaft  integral  with  the 
cam.  Above  the  cam  is  mounted  the  distributor  arm  or  rotor  which 
rotates  with  it.  The  entire  mechanism  is  arranged  so  that,  as  the 
engine  speeds  up  and  the  weights  spread  outward  against  the  resistance 


MODERN  BATTERY  IGNITION  SYSTEMS 


79 


of  the  spring,  the  ring  and  cam  are  shifted  in  a  forward  direction  in 
respect  to  the  timer  shaft.  This  has  the  effect  of  advancing  the  spark 
automatically  to  the  correct  position  in  proportion  to  the  engine  speed. 
As  the  engine  speed  decreases,  the  springs  pull  the  weights  inward 
and  the  spark  is  retarded  automatically. 

The  manual  spark  advance  lever  is  connected  to  the  spark  con- 
trol lever  on  the  steering  wheel  and  is  for  the  purpose  of  securing 
proper  timing  and  hand  control  of  the  spark  under  various  conditions 
such  as  starting,  difference  in  gasoline,  variable  weather  conditions, 
and  at  extremely  high  speeds,  requiring  spark  control  beyond  the  automatic 
advance  range.  Other  types  of  automatic  spark  advance  mechanism 
will  be  discussed  in  connection  with  the  system  on  which  it  is  used. 

71.  The  Atwater-Kent  Ignition  System,  Type  K-2.— The  Atwater- 
Kent  battery  ignition  system  is  made  in  two 
principal  types,  the  open  circuit  type  in  which 
the  interrupter  points  are  normally  open,  and 
the  closed  circuit  type  in  which  the  interrupter 
points  are  normally  closed.  The  open  circuit 
type  system  was  developed  primarily  for  use 
with  dry  cells,  while  the  closed  circuit  type 
was  developed  for  use  with  storage  battery 
and  generator. 

A  typical  model  of  the  Atwater-Kent  open 
circuit  type  system  is  the  type  K-2,  which 
has  been  widely  used  on  such  cars  as  the  Hup- 
mobile,  Peerless,  King,  Franklin,  and  Chalmers. 
Several  of  these  cars,  however,  have  recently 
changed  to  the  closed  circuit  type  Atwater- 
Kent  system  commonly  known  as  type  CC  or 
CA.  The  principal  parts  of  the  type  K-2 
system  are:  the  ignition  breaker  and  distributor  unit  or  unisparker  as 
shown  in  Fig.  94  and  Fig.  95;  and  the  non-vibrating  underhood  type 
of  induction  coil  as  shown  in  Fig.  96.  The  switch  may  be  a  simple  key 
switch  combined  with  the  lighting  switch  of  the  par  or  it  may  be  a 
special  polarity  changing  type  mounted  independent  of  the  lighting 
switch,  as  shown  in  Fig.  97,  the  function  of  which  is  to  reverse  the 
direction  of  the  primary  current  through  the  interrupter  points  each  time 
the  switch  is  turned  on. 

The  chief  feature  of  this  system  is  the  special  form  of  contact  mech- 
anism. This  is  located  immediately  below  the  distributor  as  may 
be  seen  in  Fig.  95  which  gives  an  exploded  view  of  the  entire  unit. 
The  important  feature  of  the  contact  mechanism  is  that  the  length 
of  contact  is  independent  of  engine  speed,  thus  giving  the  same  inten- 
sity of  spark  at  racing  speeds  as  when  slowly  cranking  the  engine. 


FIG.  94.— Atwater-Kent  Uni- 
sparker, Type  K-2. 


80 


AUTOMOTIVE  IGNITION  SYSTEMS 


The  action  of  the  contact  mechanism  is  shown  in  Fig.  98.     The 
four  views  show  the  movement  described  in  producing  one  spark.     The 


DISTRIBUTOR  CAP 
TERMINAL  ..^g 

RUBBER 
WASHER 
CLAMP  SCREW  ~- 

'     CONTACT  SCREW 

HOLDER  X 
INSULATED-- 
CONTACT  SCREW  ~\ 
SPRING  CONTACT  ARM—- 
LIFTER  — | 
BASE  PLATESCREW/ 
LIFTER  GUIDE  SCREW"X 
CONTACT  ARM  HOLDER 

MAIN  80 DT  CASTING — ^ 
GOVERNOR  WEIGHTS    - 
GOVERNOR  SPRINGS "4 


-DISTRIBUTOR 
BLOCK 

DISTRIBUTOR  CLAHP 

-  BINDING  POST  SCREW 
-BINDING   POST  WASHER 
-BASE  PLATE 
-LIFTER  SPRING 


-NOTCHED  SHAFT 


FIG.  95. — Construction  of  Atwater-Kent  ignition  unit,  type  K-2. 

principal  moving  parts  are:  the  hardened  steel  rotating  shaft  in  the 
center  with  as  many  notches  as  there  are  cylinders;  the  lifter;  the  latch; 


FIG.  96. — Atwater-Kent  under- 
hood  coil. 


FIG.  97. — Atwater-Kent  polarity  reversing 
ignition  switch. 


and  the  contact  spring.     The  contact  points  are  normally  open.     The 
contact  is  made  and  broken  by  the  action  of  the  lifter  spring  in  draw- 


MODERN  BATTERY  IGNITION  SYSTEMS  81 

ing  the  lifter  back,  or  after  the  lifter  has  become  unhooked  from  the 
notched  shaft.  When  the  lifter  is  pulled  forward  by  the  notched 
shaft,  it  does  not  touch  the  latch.  It  is  pulled  forward  until  it  reaches 
a  point  where  it  unhooks  from  the  notched  shaft  and  is  then  snapped 
back  by  the  lifter  spring,  striking  the  latch  as  it  returns.  The  latch, 
being  struck  by  the  lifter,  presses  against  the  contact  spring  and  closes 
the  points  for  a  brief  instant,  opening  immediately  after  the  lifter  passes. 
With  the  latch  and  lifter  returned  to  their  original  position,  the  mech- 
anism is  again  ready  to  repeat  the  same  operation  for  producing  the  next 
spark.  The  spring  action  makes  the  speed  of  the  break  independent  of 
the  speed  of  the  engine.  It  also  makes  the  time  of  contact  uniform, 
and,  since  the  period  of  contact  is  so  brief,  the  system  draws  the  least 
possible  current  from  the  batteries.  This  makes  it  particularly  adapted 
for  use  with  dry  cells. 

It  is  while  the  contacts  are  making  momentary  contact  that  the 
current  flows  through  the  primary  winding  of  the  ignition  coil.     Then, 


FIG.  98. — Operation  of  Atwater-Kent  contact  mechanism  for  type  K-2  ignition  system. 

when  the  points  separate,  the  coil  demagnetizes  and  a  high-voltage 
current  is  induced  in  the  secondary  winding.  The  secondary  current 
is  led  to  the  center  terminal  of  the  distributor,  from  which  point  it  is 
directed  to  the  various  spark  plugs  in  their  proper  order  of  firing  by 
the  revolving  distributor  block,  Fig.  99. 

Owing  to  the  very  short  period  in  which  the  contacts  are  together 
and  the  consequent  short  duration  of  the  current  flow,  the  coil  used 
with  such  an  interrupter  must  be  designed  to  magnetize  or  build  up 
very  rapidly.  This  is  due  to  the  fact  that  it  requires  an  appreciable 
amount  of  time  for  the  primary  current  to  rise  to  its  full  value,  depend- 
ing upon  the  quality  and  shape  of  the  core,  and  the  number  of  turns 
and  size  of  wire  in  the  primary  coil  winding.  Thus  it  will  be  seen  that 
an  induction  coil  designed  to  operate  with  an  interrupter  of  the  closed 
circuit  type  will  not  operate  satisfactorily  with  one  of  the  open  circuit  type 
since  the  points  will  open  before  the  core  becomes  fully  magnetized.  On 
the  other  hand,  a  coil  intended  for  the  open  circuit  type  interrupter 
will  be  of  too  low  resistance  to  give  satisfactory  service  with  a  closed 


82 


AUTOMOTIVE  IGNITION  SYSTEMS 


circuit  type  of  breaker,  as  the  current  flow  will  be  abnormally  high, 
usually  causing  rapid  burning  of  the  contact  points  and  possible  injury 
to  the  condenser. 

A  complete  wiring  diagram  of  the  type  K-2  system  using  a  switch 
of  the  polarity  changing  type  is  shown  in  Fig.  99.  .The  switch  has 
two  positions  "OFF"  and  "ON."  When  the  switch  is  turned  "ON," 
if  terminal  B  is  connected  to  S}  and  Bf  to  $',  the  current  will  flow  as 
indicated  by  the  arrows.  The  next  time  the  ignition  is  turned  on, 
by  turning  the  switch  another  quarter  turn  in  the  same  direction,  the 
connections  in  the  switch  are  reversed,  connecting  B  to  S',  and  B'  to 
S.  This  reverses  the  direction  of  the  primary  current  through  the 
unisparker.  The  purpose  of  this  is  to  equalize  the  transfer  of  metal 


(FIRING  ORDER     «-*  -2-0  -3-5") 
CONDENSER 


IGNITION    SWITCH 
(POLARITY  CHANGING  TYPE] 


UNISPARKER 


•sft- 

FIG.  99. — Wiring  diagram  for  Atwater-Kent  ignition  system,  type  K-2. 


by  the  action  of  the  spark  at  the  point  of  contact,  thereby  decreasing 
the  wear  and  prolonging  the  life  of  the  points. 

Contact  Point  Adjustment. — The  normal  gap  between  the  contact 
points  is  from  .010  in.  to  .012  in. — never  closer.  When  the  gap  becomes 
too  wide,  due  to  wear,  the  engine  will  be  hard  to  start  and  will  fire  ir- 
regularly. The  head  of  the  contact  screw,  Fig.  99,  is  set  up  against 
several  thin  washers.  A  sufficient  number  of  these  washers  should  be 
removed  to  give  the  correct  gap  when  the  screw  is  set  up  tight. 

The  contact  points  are  made  of  purest  tungsten,  a  material  which  is 
many  times  harder  than  platinum.  When  the  contact  points  are  working 
properly,  small  particles  of  tungsten  are  carried  from  one  point  to  the 
other,  sometimes  forming  a  rough  surface,  characterized  by  a  dark  gray 
color.  This  roughness  does  not  in  any  way  affect  the  proper  working 


MODERN  BATTERY  IGNITION  SYSTEMS 


83 


of  the  points,  owing  to  the  fact  that  the  rough  surfaces  fit  into  each  other 
perfectly.  However,  when  it  becomes  necessary  to  take  up  the  distance 
between  these  points,  due  to  natural  wear,  it  is  advisable  to  remove  both 
contact  screw  and  spring  contact  arm,  and  dress  down  the  high  spots 
with  an  oil  stone  or  a  new  fine  file.  This  makes  it  possible  to  obtain  a 
more  accurate  adjustment  and  eliminates  danger  of  any  high  points  on 
the  contacts  touching  each  other  when  the  parts  are  at  rest. 

Automatic  Spark  Advance  Mechanism. — The  mechanism  for  automa- 
tically advancing  and  retarding  the  spark,  as  shown  in  Fig.  100,  is 
located  in  the  housing  immediately  below  the  interrupter.  It  consists 
of  a  system7 of  weights  and  springs  or  governor  arranged  so  as  to 
advance  the  spark  automatically  as  the  engine  speed  increases.  The 


Motor  stopped  or  running  slowly.  Motor  at  high  speed. 

FIG.   100. — Atwater-Kent  automatic  spark  advance  mechanism. 


timer  shaft  is  divided,  the  upper  portion  being  notched  for  operating  the 
contact  mechanism.  As  the  speed  increases,  the  weights  fly  outwardly, 
due  to  centrifugal  force,  shifting  the  upper  part  of  the  shaft  more  and 
more  ahead  of  the  lower  or  driving  shaft,  thus  causing  contact  to  occur 
earlier  and  thereby  advancing  the  spark.  The  relative  positions  of  the 
governor  weights  at  high  and  low  speeds  are  shown  in  Fig.  100.  As  the 
speed  of  the  engine  is  reduced,  the  pull  of  the  springs  causes  the  weights 
to  move  inwardly,  turning  the  upper  or  notched  end  of  the  shaft  back- 
ward, or  reverse  to  the  direction  of  rotation  of  the  driving  shaft,  thereby 
retarding  the  spark.  The  total  amount  of  automatic  spark  advance  at 
high  speed  is  from  30°  to  40°.  This  is  indicated  in  Fig.  100  by  the  posi- 
tion of  the  offset  slot  in  the  top  of  the  notched  shaft  shown  in  the  right- 
hand  view  compared  with  that  in  the  left-hand  view  which  shows  its 
low  speed  position. 


84  AUTOMOTIVE  IGNITION  SYSTEMS 

Timing  the  Spark. — Since  the  type  K-2  is  not  generally  used  with  a 
spark  control  lever  it  should  be  installed  so  as  to  allow  a  small  amount  of 
angular  movement  for  the  initial  timing  adjustment.  In  other  words, 
the  socket  into  which  the  unisparker  fits  should  be  provided  with  a  clamp 
which  will  permit  the  unisparker  to  be  turned  and  locked  rigidly  in  any 
given  position. 

In  timing,  the  piston  in  No.  1  cylinder  should  be  raised  to  upper  dead 
center  between  compression  and  power  strokes.  The  clamp  which  holds 
the  unisparker  should  then  be  loosened  and  the  unisparker  (the  entire 
ignition  unit)  slowly  and  carefully  turned  backwards  or  counterclockwise 
(opposite  in  direction  to  the  rotation  of  the  timer  shaft)  until  a  click  is 
heard.  This  click  occurs  at  the  exact  instant  of  the  spark.  At  this 
point,  the  unisparker  should  be  clamped  and  care  taken  not  to  change  its 
position.  The  distributor  cap,  which  fits  only  in  one  position,  should 
then  be  removed  and  the  position  of  the  distributor  block  on  the  end  of 
the  shaft  noted.  The  terminal  to  which  it  points  must  be  connected  to 

No.  1  cylinder.  The  other  cylinders  should 
then  be  connected  in  turn  to  the  other 
terminals  in  their  proper  order  of  firing,  bear- 
ing in  mind  the  direction  of  rotation  of  the 
timer  shaft. 

When  timed  in  this  manner,  the  spark  will 
occur  in  each  cylinder  exactly  on  dead  center 
if  the  engine  is  turned  over  slowly.  At  crank- 
ing speeds  and  for  safe  starting,  the  spark  is 

FlG'  *  ignl"  retarded  automatically  by  the  governor,  and, 

as  the  speed  increases,  the  spark  is  advanced 
automatically,  thus  requiring  no  attention  on  the  part  of  the  driver. 

72.  The  Atwater-Kent  Ignition  System,  Type  CC.— The  Atwater- 
Kent  ignition  system  type  CC  is  of  the  closed  circuit  type  developed  for 
use  on  cars  equipped  with  electric  starting  and  lighting  equipment  and 
is  intended  to  operate  on  current  from  a  storage  battery.  It  consists 
of  a  breaker  and  distributor  unit  mounted  with  a  non-vibrating  coil  on 
a  base  as  shown  in  Fig.  101.  The  unit  has  the  same  general  dimensions 
as  the  standard  high-tension  magneto  and  is  driven  in  the  same  manner. 
For  this  reason  it  is  termed  a  magneto  replacement  unit.  Figure  102 
shows  the  Atwater-Kent  installation  on  the  1918  Maxwell  engine. 

The  principal  feature  of  the  system  lies  in  the  design  of  the  breaker 
mechanism  as  shown  in  Fig.  103.  The  contact  maker  consists  of  an 
exceedingly  light  steel  contact  arm,  the  end  of  which  rests  lightly  on  a 
hardened  steel  cam  which  rotates  at  one-half  crankshaft  speed.  The 
other  end  of  the  contact  arm  is  grounded  permanently  to  the  base  through 
the  spring  which  carries  the  contact  arm.  This  has  an  advantage  in  that 
there  is  no  pivot  which  the  arm  swings  on,  to  wear  and  otherwise  cause 


MODERN  BATTERY  IGNITION  SYSTEMS  85 

trouble.  The  normal  gap  between  the  breaker  points  should  not  be  less 
than  .005  in.  nor  more  than  .008  in.  The  standard  setting  is  .006  in.  This 
is  about  the  thickness  of  two  pages  of  this  book. 


FIG.   102. — Atwater-Kent  type  CC  ignition  system  mounted  on   1918  Maxwell  engine. 

For  use  on  four-cylinder  engines,  the  cam  has  four  lobes  which  open 
the  contact  points  four  times  for  each  revolution  of  the  timer  shaft  or 
twice  for  each  revolution  of  the  engine  crankshaft.  Each  time  the  con- 


FIG.  103. — Atwater-Kent  breaker       FIG.  104. — Construction  of  Atwater-Kent 
mechanism,  type  CC.  distributor  head,  type  CC. 

tact  points  are  opened,  the  primary  circuit  of  the  ignition  system  is  inter- 
rupted, thus  producing  a  discharge  of  secondary  high-tension  current  at 
one  of  the  spark  plugs.  The  secondary  spark  occurs  when  the  contacts 
separate. 


86 


AUTOMOTIVE  IGNITION  SYSTEMS 


The  distributor  head,  a  section  of  which  is  shown  in  Fig.  104,  forms 
the  top  of  the  ignition  unit.  Each  spark  plug  wire  terminates  in  an 
electrode  which  passes  through  the  distributor  cap.  A  rotating  dis- 
tributor block  takes  the  high-tension  current  from  the  center  terminal  of 
the  distributor  and  distributes  it  to  the  plugs  in  the  proper  firing  order. 
The  distributor  block  just  clears  the  distributor  points  without  actually 
touching.  The  high-tension  current  jumps  this  small  gap  without  ap- 
preciable loss.  • 

In  Fig.  105  is  shown  a  complete  circuit  diagram  of  the  usual  type  CC 
installation.  In  some  cases,  the  ignition  switch  may  be  combined  with 
the  lighting  switch.  With  the  switch  shown,  the  primary  circuit  is 


IGNITION  SWITCH 


—  DISTRIBUTOR 


GROUND 


GROUND 


BREAKER 


FIG.   105. — Wiring  diagram  for  Atwater-Kent  ignition  system,  type  CC. 

complete  when  the  ignition  button  is  pushed  in,  the  arrows  indicating 
the  path  of  the  current.  A  resistance  unit  is  mounted  in  the  top  of  the 
coil  housing  to  provide  protection  for  the  coil  and  battery  in  case  the 
switch  is  left  on.  It  also  assists  in  equalizing  the  secondary  spark  at 
high  and  low  engine  speeds  as  previously  explained. 

The  Condenser. — The  condenser  is  mounted  directly  on  the  timer 
base  beside  the  breaker,  the  electrical  connections  to  the  breaker  contacts 
being  as  shown  in  Fig.  105.  The  method  of  condenser  installation  is 
shown  in  Fig.  106.  The  condenser  has  two  flat  copper  terminals  which 
are  clamped  under  the  screws  which  hold  the  condenser  cover  in  place. 
In  installing  the  condenser,  one  copper  terminal  A  should  be  clamped 
under  the  insulating  washer  3  so  as  to  force  it  in  contact  with  the  bright 


MODERN  BATTERY  IGNITION  SYSTEMS 


87 


metal  surface  of  the  timer  base  plate  thus  grounding  terminal  A.  The 
other  terminal  B  is  forced  against  the  upper  condenser  cover  plate  4  on 
the  side  adjacent  to  the  breaker  connection  screw.  This  cover  plate 
is  insulated  from  the  base  plate; 
consequently,  terminal  B  is  in- 
sulated from  the  ground  and 
makes  electrical  connection  with 
the  adjustable  contact  7. 

The  sequence  of  operations  in 
installing  the  condenser  is  as 
follows : 

1.  Insulated    washer   placed 
in  position. 

2.  Condenser    placed    in 
pocket. 

3.  Insulated  washer  No.  3  is 
laid  on  top  of  condenser  terminal. 

4.  Condenser    cover    No.    4 
placed  in  position. 

5.  Insulated  screws  put  in. 
Note  that  contact  adjustment 

is  corrected;  that  is,  the  points 
meet  squarely  and  open  a  maxi- 
mum distance  of  .006  in.  to  .008 


in. 


FIG.  106. — Installation  of '  Atwater-Kent  con- 
'  denser,  type  CC. 


Timing. — The  method  of  timing  the  ignition  unit  with  the  engine  is 
practically  the  same  for  four-,  six-,  or  eight-cylinder  engines  since  by 
timing  the  spark  in  one  cylinder  the  rest  will  be  in  proper  time.     The 
,  following  procedure  should  be  followed  in  timing  a 
four-cylinder    automobile    engine    equipped    with 
Atwater-Kent  ignition,  type  CC,  such  as  used  on 
the  Maxwell  models  1917  to  1920   in  which  the 
ignition  unit  is  driven  by  a  slotted  coupling  as 
shown  in  Fig.  107. 

After  making  sure  that  all  the  advance  rods  and 
electrical  connections  are  complete,  and  that  the 
advance  rods  are  so  adjusted  as  to  allow  a  full 
FIG.   107.— Atwater-    movement  of  the  breaker  head  for  the  full  move- 
Kent  ignition  unit  drive    ment  Of  the  advance  lever,  proceed  as  follows: 

coupling. 

1.  After  all  ignition  wiring  is  complete,  includ- 
ing the  connections  to  the  plugs,  as  in  Fig.  105,  remove  all  plugs  and  lay 
them  in  order  on  the  top  of  the  cylinder  casting,  leaving  the  plug  wires 
attached.  Make  sure  that  the  terminal  ends  of  the  spark  plugs  do  not 
touch  the  engine  frame. 


88 


AUTOMOTIVE  IGNITION  SYSTEMS 


2.  With  the  ignition  switch  "ON, "  crank  the  engine  slowly  by  hand 
and  note  that  each  spark  plug  sparks  in  its  proper  order  (1,  3,4,  2  for 
Maxwell),  turning  "OFF"  the  ignition  when  this  is  checked. 

3.  Set  the  spark  lever  on  the  steering  wheel  about  \y±  in.  from  "full 
retard"  position. 

4.  Loosen  the  ignition  timer  coupling  so  that  the  collar  on  the  hori- 
zontal shaft,  Fig.  107,  may  be  easily  turned. 

5.  Crank  the  engine  slowly  by  hand  until  the  piston  in  No.  1  cylinder 
is  on  upper  dead  center  firing  position.     In  this  position  the  notch  in  the 
drive-shaft  half  of  the  coupling  should  be  up. 

6.  Turn  the  ignition  switch  "ON." 

7.  With   the   fingers    or   with  the  point  of  a  screwdriver  turn  the 
collar  to  the  right  slowly  and  carefully 

until  a  spark  jumps  across  No.  1  plug  as 
it  lays  exposed  on  the  cylinder,  stopping 


BRASS  GROUNDING  STRIP 


SAFETY 
GAP 


FIG.   108. — Connecticut  igniter,  model 
16C. 


FIG.   109. — Connecticut  coil  showing  spark  gap 
and  connections. 


at  the  instant  the  spark  occurs.  In  case  it  should  be  turned  past  the 
correct  point,  give  the  collar  a  quarter  turn  back  and  try  it  slowly  and 
carefully  again  until  it  is  stopped  at  the  right  point. 

8.  Lock  the  adjustment  by  tightening  the  hexagonal  screw  on  the 
coupling  clamp,  and  screw  the  spark  plugs  into  place. 

The  engine  is  now  timed  so  that  the  spark  occurs  with  No.  1  cylinder 
on  dead  center  when  the  spark  lever  is  within  lj^  in.  of  "full  retard." 
This  will  allow  about  10°  retard  for  safe  starting  and  smooth  idling 
and  about  20°  advance  for  high  speeds. 

73.  The  Connecticut  Battery  Ignition  System. — The  principal  parts 
of  the  Connecticut  battery  ignition  system  consist  of  an  igniter,  Fig.  108, 
a  non-vibrating  induction  coil,  Fig.  109,  and  a  switch  of  special  construc- 
tion, typical  examples  of  which  are  shown  in  Fig.  110  and  Fig.  111. 


MODERN  BATTERY  IGNITION  SYSTEMS 


89 


The  igniter,  details  of  which  are  shown  in  Fig.  112  and  Fig.  113, 
operates  on  the  closed  circuit  principle,  the  primary  circuit  being  inter- 
rupted or  broken,  and  the  secondary  spark  produced  when  the  lobes  of 
the  cam  strike  the  roller  of  the  contact  arm,  separating  the  contact 


FIG.   110. — Front  and  rear  views  of  Connecticut  combination  lighting  and  ignition  switch, 

type  H-ND. 

points.  The  cam  has  as  many  lobes  as  there  are  cylinders  and  rotates 
at  one-half  crankshaft  speed.  The  distributor  arm,  which  directs  the 
secondary  current  to  the  various  plugs  in  their  proper  order  of  firing,  is 


FIG.   111. — Internal  view  of  Connecticut  automatic  ignition  switch,  type  H. 

carried  above  the  cam  on  the  upper  end  of  the  same  shaft.  In  most 
installations,  the  igniter  is  mounted  on  the  side  of  the  engine  and  is 
driven  through  spiral  gears  from  one  end  of  the  generator  shaft. 

The  coil,  which  also  houses  the  condenser,  is  mounted  close  to  the 


90 


AUTOMOTIVE  IGNITION  SYSTEMS 


igniter  on  the  engine  frame,  or  on  top  of  the  generator,  and  is  connected 
to  the  breaker  by  short  flexible  leads.  One  side  of  the  condenser,  as  well 
as  one  side  of  the  primary  and  secondary  winding,  is  grounded  through 


FIG.   112. — Connecticut  igniter  with  distributor  head  removed  showing  breaker  mechanism, 

models  16  and  16C. 

the  brass  strip  on  the  side  of  the  coil  to  the  coil  base  and  engine  frame. 
The  condenser,  although  mounted  in  the  coil,  is  connected  electrically 


FIG.  113. — Connecticut  igniter  with  distributor  head  removed  showing  breaker  mechanism, 

models  16  and  16C. 

across  the  interrupter  points  through  the  two  short  leads  which  connect 
the  coil  with  the  igniter.  Its  purpose  is  to  protect  the  points  against 
pitting  as  previously  explained. 


MODERN  BATTERY  IGNITION  SYSTEMS 


91 


One  of  the  distinct  features  of  the  Connecticut  ignition  system  is  the 
switch  which  is  provided  with  an  automatic  "kick  out"  mechanism  for 
releasing  the  switch  and  thus  opening  the  primary  battery  circuit  in  case 
the  switch  should  be  accidentally  left  on  with  the  engine  not  running. 
The  purpose  of  this  is  to  safeguard  against  undue  draining  of  the  battery 
and  to  prevent  overheating  of  the  ig'nition  coil. 

The  switch  is  made  in  two  principal  models  known  as  type  H,  Fig. 
Ill,  and  type  K,  Fig.  114,  the  latter  being  of  the  latest  design  as  intro- 
duced on  many  1919  and  1920  cars.  When  the  switch  is  mounted  in- 
tegral with  the  lighting  switch,  the  complete  switch  unit  or  panel  is 
known  as  type  H-ND  and  KVD,  respectively,  as  shown  in  Fig.  110  and 

Fig.  115. 

A  complete  circuit  diagram  of  the 
Connecticut  system  using   the   type 
H-ND  switch  is  shown  in  Fig.  116. 
_        |r     i^rar  When   the   ignition  button  (the  left- 


FIG.  114. — Connecticut  automatic  igni- 
tion switch,  type  K. 


FIG.  115. — Rear  view  of  Connecticut  com- 
bination ignition  and  lighting  switch,  type 
KVD. 


hand  button  to  the  driver)  is  pushed  in,  the  primary  current  from 
the  battery  completes  its  circuit  as  indicated.  The  current  flows  from 
the  positive  battery  terminal  to  the  switch  terminal  B,  then  through  the 
switch  contacts  and  resistance  element  to  the  switch  terminal  C  which 
is  connected  to  the  terminal  C  on  the  ignition  coil.  The  current  then 
flows  through  the  primary  winding  of  the  coil  to  the  stationary  side  of 
the  igniter,  across  the  breaker  points  to  the  grounded  terminal  of  the 
coil,  returning  to  the  negative  terminal  of  the  battery  through  the  ground. 
The  current  induced  in  the  secondary  winding  of  the  coil,  upon  interrup- 
tion of  the  primary,  flows  from  the  secondary  winding  to  the  center  of  the 
distributor,  through  the  distributor  arm  to  the  spark  plug,  across  the 
plug,  and  back  to  the  grounded  coil  terminal.  It  will  be  noted  that  a 
safety  gap  is  provided  in  the  top  end  of  the  coil.  It  is  enclosed  in  a  mica 


92 


AUTOMOTIVE  IGNITION  SYSTEMS 


tube  inaccessible  to  vapor  or  fumes  yet  is  under  a  mica  window  so  that 
the  spark  may  be  readily  observed  in  the  case  of  a  misfiring  cylinder. 
The  purpose  of  this  gap,  as  previously  explained,  is  to  protect  the  second- 
ary winding  from  the  destructive  action  of  the  high  voltage,  in  case  a  plug 
terminal  should  become  disconnected  and  the  high-tension  current  thus 
prevented  from  taking  its  regular  path.  The  ignition  is  turned  off  by 
simply  pushing  in  on  the  "OFF"  button,  which  will  release  latch  G  allow- 
ing the  "ON"  button  to  fly  out  and  the  switch  contacts  to  open. 

Operation  of  Automatic  Switch,  Type  H. — A  study  of  Fig.  116  will  also 
show  the  principle  of  the  automatic  switch  mechanism.  The  thermostat 
consists  of  two  strips  of  dissimilar  metals,  nickel  steel  and  spring  brass, 
welded  along  their  entire  surface  and  wound  with  a  heating  element 
similar  to  that  used  for-  resistance,  units.  Brass  expands  with  increase 


TO  SPARK    PLUGS 


LIGHTING  SWITCH        IGNITION    SWITCH 
KEY         OFF         ON 


FIG.  116. — Wiring  diagram  of  Connecticut  battery  ignition  system,  wiring  type  H  ignition 

switch. 

in  'temperature  much  more  rapidly  than  nickel  steel;  consequently,  the 
thermostat  blade,  which  is  fixed  at  one  end,  will  bend  as  it  is  heated  up  in 
proportion  to  the  increase  in  temperature.  The  resistance  unit  is  in  the 
primary  ignition  circuit. 

In  case  the  switch  is  left  on  with  the  engine  not  running  and  the 
breaker  points  closed,  the  continuous  flow  of  current  through  the  resist- 
ance unit  will  cause  the  thermostat  blade  to  heat  up  and  bend  sufficiently 
to  close  the  contacts  E.  This  will  complete  a  circuit  from  the  battery 
through  the  winding  of  the  electromagnet  causing  the  arm  F  to  vibrate 
rapidly.  The  end  of  arm  F  upon  striking  the  lever  G,  automatically 
releases  the  switch  button.  The  thermostat  can  be  adjusted  to  operate 
at  any  time  from  30  seconds  to  4  minutes.  This  adjustment  is  made  after 
the  engine  stops  by  varying  the  gap  of  the  thermostat  contacts.  The  nor 


MODERN  BATTERY  IGNITION  SYSTEMS 


93 


mal  setting  should  be  such  as  to  release  the  switch  in  about  three-quarters 
of  a  minute  after  the  engine  has  stopped. 

Operation  of  Automatic  Switch,  Type  K. — The  automatic  switch,  type 
K,  differs  from  type  H,  principally  in  the  arrangement  of  the  thermostats, 
two  being  employed  instead  of  one,  and  in  the  method  of  releasing  the 
switch  button,  as  may  be  seen  by  comparing  Fig.  Ill  and  Fig.  114.  A 
circuit  diagram  of  a  typical  ignition  system  using  the  type  K  switch  is 
shown  in  Fig.  117.  Referring  to  Fig.  114  and  Fig.  117,  the  operation  of 
this  switch  is  as  follows :  With  the  switch  button  plunger  c  pushed  in,  the 
contacts  h  are  closed  and  the  primary  circuit  is  completed  through  the 
thermostatic  bar  6  and  heater  tape  e,  the  current  entering  the  switch  at 

AUTOMATIC   IGNITION    SWITCH 


ADJUSTABLE    INSULATED 
"CONTACT    POINT—  "f" 


GROUND   15 

AUTOMATICALLY 

MADE   OH   MOUNTING 

,BAND 


FIG.   117. — Wiring  diagram  of  Connecticut  battery  ignition  switch  using  type  K  switch. 

terminal  B  and  leaving  at  terminal  C  as  indicated.  The  switch  button  is 
held  in  by  a  fiber  wedge-shaped  block  mounted  on  the  free  end  of  a 
second  thermostatic  bar  d  the  fixed  end  of  which  is  grounded  to  the  switch 
case  and  electrically  connected  to  terminal  G  which  is  also  grounded.  If 
the  switch  is  left  on  and  an  uninterrupted  flow  of  current  is  allowed  to 
pass  through  the  heater  tape  e,  the  thermostatic  bar  6  will  bend  down  until 
it  makes  contact  on  adjustment  screw  /.  This  will  allow  current  to  flow 
from  the  battery  through  the  heater  tape  g  to  the  ground  post  G  causing 
the  thermostatic  latch  d  to  bend  up  sufficiently  to  release  the  switch 
button  plunger  c,  thus  opening  the  switch  contacts  h.  The  switch  can 
be  also  turned  off  by  pulling  plunger  c  which  will  release  the  latch  and 
accomplish  the  same  result. 


94 


AUTOMOTIVE  IGNITION  SYSTEMS 


The  time  in  which  the  switch  will  release  itself  after  the  engine  has 
stopped  may  be  regulated  by  turning  the  adjustment  screw/.  The  time 
for  release  may  be  increased  by  increasing  the  gap  between  the  contacts 
slightly,  and  the  time  decreased  by  decreasing  the  gap  slightly.  The 
normal  adjustment  should  be  such  that  release  of  the  switch  will  occur  in 
about  three-fourths  of  a  minute,  the  same  as  for  the  switch  type  H. 

The  breaker  mechanism  is  very  simple  as  Fig.  116  shows.  In 
operation,  the  rotation  of  the  cam  C  causes  it  to  strike  the  fiber  roller  R 
thus  lifting  the  arm  A  and  separating  the  contact  points.  The  arm  is 
returned  to  its  normal  position  by  a  flat  spring  attached  to  the  contact 
arm. 

The  breaker  mechanism  is  mounted  on  a  plate  which  rests  in  the 
casing  and  is  held  in  place  by  a  spring  ring  and  also  by  a  solid  ring,  the 
latter  being  held  by  two  screws  as  shown  in  Fig. 
113.  The  advance  lever  engages  a  pin  on  the 
breaker  plate,  the  whole  plate  being  advanced 
around  the  shaft  to  advance  the  time  of  ignition. 
The  contacts  should  be  adjusted  to  open  .020  in. 
Inasmuch  as  the  system  operates  on  the  closed 
circuit  principle,  the  maximum  time  is  allowed 
for  the  complete  magnetization  of  the  induction 
coil.  The  intensity  of  the  sparks  produced  at 
the  plugs  depends  upon  this  magnetization.  It 
follows  that  the  slower  the  speed  of  the  engine 
the  greater  the  magnetization  of  the  core  and 
the  greater  the  spark  intensity.  However,  this 
is  partly  counteracted  by  the  action  of  the  re- 
sistance unit  surrounding  the  thermostat.  This 
resistance  unit  tends  to  equalize  the  intensity  of 
the  secondary  spark  at  high  and  low  engine 
speeds  in  the  same  way  as  the  resistance  units  on  other  systems. 

74.  The  Remy  Ignition  System. — The  Remy  battery  ignition  system, 
which  is  of  the  high-tension  distributor  type,  consists  principally  of  a 
vertical  breaker  unit,  Fig.  118;  a  non- vibrating  coil,  a  typical  design  of 
which  is  shown  in  Fig.  119;  and  a  switch  which  may  be  of  either  the  plain 
or  polarity  changing  type.  The  ignition  switch  is  often  combined  with 
the  lighting  switch. 

One  type  of  Remy  ignition  system  which  has  been  used  very  exten- 
sively is  that  shown  in  Fig.  120.  In  this  system  the  breaker  is  driven 
from  the  generator  shaft  through  spiral  gears  and  the  coil  is  mounted 
close  by  on  the  generator  frame.  The  coil  is  supported  by  a  special 
bracket  which  also  serves  to  ground  one  side  of  both  the  primary  and  the 
secondary  windings.  The  breaker  operates  on  the  closed  circuit  prin- 
ciple and  is  very  simple  in  construction  as  may  be  seen  from  Fig.  121. 


FIG.  118. — Remy  battery 
ignition  breaker  and  dis- 
tributor unit. 


MODERN  BATTERY  IGNITION  SYSTEMS 


95 


The  interrupter  comprises  two  contact  points  of  platinum-indium  or 
tungsten,  usually  the  latter,  one  being  stationary  while  the  other  is 
carried  at  the  free  end  of  a  pivoted  lever  which  bears  against  the  rotating 
steel  cam.  The  cam  has  accurately  ground  corners  (one  for  each  cylin- 
der) which  bear  against  the  fiber  block  on  the  lever  in  rotation  and  cause 


:    BATTERY   WIRE  ' 
.FROM16NITION  SWITCH 


SECONDARY    • 
WIRE  TO  CENTER  - 
OF  DISTRIBUTOR 


-~-W!R£  TO  INSULATED 
BREAKER  TERMINAL 


COIL  BASE  GROUNDED 
ON  ENGINE  FRAME    , 


FIG.   119. — Remy  induction  coil — two  primary  terminal  type. 

the  contact  points  to  open  and  close  at  correct  intervals.  The  cam  has 
as  many  lobes  as  the  engine  has  cylinders  and  is,  therefore,  driven  at  one- 
half  crankshaft  speed.  The  high-tension  current  is  distributed  to  the 
spark  plug  leads  by  a  distributor  brush  which  is  carried  above  the  cam 
but  does  not  touch  the  pins  in  the  distributor  head. 


IGNITION    BREAKER 
AND  DISTRIBUTOR  UWT ,. 


PRIMARY  TERMINALS 
INDUCTION  COIL 


RESISTANCE  UNIT 


FIG.  120. — Remy  generator  with  ignition  coil  and  distributor  mounted. 

The  distributor  brush  in  some  models  also  carries  the  safety  gap  which 
is  a  gap  of  %  in.  between  the  distributing  segment  and  the  bottom  plate 
which  is  grounded  upon  the  shaft.  This  provides  a  safety  gap  across 
which  the  spark  can  discharge  in  case  any  of  the  connections  from  the  dis- 
tributor to  the  spark  plug  should  become  broken.  The  destruction  of  the 


96 


AUTOMOTIVE  IGNITION  SYSTEMS 


coil  windings  due  to  excessive  voltage  is  thus  prevented.  The  safety  gap 
should  not  be  less  than  ^2  m-  as  the  spark  might  then  discharge  across 
it  instead  of  across  the  spark  plug  gap  when  the  plug  is  under  compres- 
sion. Some  of  the  distributor  units  are  equipped  with  an  automatic 
spark  advance  in  which  case  the  governor  mechanism  is  mounted  in  the 
housing  below  the  cam.  The  advance  of  the  spark  is  provided  by  the 


CONTACT 

ARM 


BREAKER 
POINTS 


SAFETY 
GAP 


CAM 


FIG.   121. — Remy  breaker  and  distributor. 

revolving  weights  which  spread  more  and  more  due  to  centrifugal  force 
and  shift  the  cam  in  an  advance  direction.  As  the  engine  slows  down, 
the  cam  is  shifted  in  the  reverse  direction  and  the  spark  is  retarded. 

Two  types  of  coils  are  used.  One  has  two  primary  terminals  on  top, 
as  shown  in  Fig.  119,  in  which  case  the  coil  operates  with  a  simple  switch 
of  the  "ON"  and  "OFF"  type,  while  the  other  has  three  primary  termi- 


TO    SPARK    PLUGS 


SIMPLE  KEY  SWITCH 


DISTRIBUTOR 


FIG.   122. — Wiring  diagram  for  Remy  battery'ignition  system  using  two  primary  terminal 

coil. 

nals  on  top  as  shown  in  Fig.  120  and  operates  with  a  four- terminal  switch 
of  the  polarity  changing  type.  In  both  cases  the  condenser  is  placed 
inside  the  coil  and  a  resistance  unit  is  mounted  on  top  for  controlling 
the  primary  current.  Figure  122  shows  a  typical  wiring  diagram  of  the 
Remy  system  using  the  two-terminal  coil,  and  Fig.  123  shows  a  typical 
wiring  diagram  of  the  system  using  the  three-terminal  coil. 


MODERN  BATTERY  IGNITION  SYSTEMS 


97 


The  purpose  of  the  polarity  changing  type  switch  is  to  reverse  the 
direction  of  current  flow  across  the  breaker  points  each  time  the  ignition 
is  used.  It  is  absolutely  necessary  that  the  ignition  switch  be  placed  in 
the  "OFF"  position  when  the  engine  is  not  running.  If  it  is  left  in  the 
"ON"  position,  current  from  the  storage  battery  will  discharge  through 
the  ignition  coil.  If  this  discharge  continues,  the  battery  will  be  ex- 


TO  SPARK     PLUGS 


IGNITION   SWITCH 

OLARITY    CHANGING  TY 


DISTRIBUTOR 


(POLARITY 


NGING  TYPE} 


Correct 


Incorrect 


FIG.  123. — Wiring  diagram  for  Remy  battery  ignition  system  using  three  primary  termina 

coil. 

hausted.  To  aid  in  preventing  theft  or  unauthorized  use,  the  operator 
should  remove  the  switch  key  when  leaving  the  car. 

Adjustment  of  Contact  Points. — The  contact  points  should  have  a 
maximum  opening  of  .020  in.  to  .025  in.,  or  the  thickness  of  the  gage  which 
is  on  the  side  of  the  wrench  furnished  for  adjusting  the  contact  point 
opening.  It  is  recommended  that  an  inspection  of  the  points  be  made 
every  1000  miles.  If  the  points  are 
found  to  be  worn  unevenly  or  are 
dirty,  they  may  be  cleaned  by  pass- 
ing a  fine  flat  file,  or  preferably  a 
piece  of  No.  00  sandpaper,  between 
them.  When  the  contacts  are  prop- 
erly fitted,  they  should  make  clean 
square  contact  as  shown  by  A  in  Fig. 
124.  Adjustment  of  the  gap  between 
the  contacts  is  made  by  loosening  the 
lock  nut  with  the  wrench  furnished, 

turning  the  adjusting  screw,  and  then  locking  the  nut  again.  These  con- 
tact points  should  not  be  oiled.  A  slight  trace  of  vaseline  placed  on  the 
fiber  block  or  on  the  cam  every  1000  miles  will  keep  the  cam  from  rusting. 

Timing  Ignition  to  the  Engine. — The  time  of  opening  the  breaker 
contact  points  relative  to  the  travel  of  the  piston  is  determined  as  follows : 
The  distributor  advance  lever  is  pushed  back  to  full  retard  position.  The 


FIG.  124. — Correct  and  incorrect  shapes  for 
battery  breaker  contact  points. 


98  AUTOMOTIVE  IGNITION  SYSTEMS 

engine  is  brought  to  dead  center  position  with  No.  1  piston  at  the  top  of 
its  compression  stroke.  Dead  center  is  accurately  indicated  when  the 
line  U.  D.  C.  on  the  flywheel  is  opposite  the  corresponding  prick-punch 
mark  on  the  engine  frame.  In  this  position  of  the  flywheel  the  pistons 
in  both  of  the  two  cylinders  indicated  by  the  numerals  after  U.  D.  C. 
will  be  at  the  top  of  the  stroke.  By  holding  the  finger  over  the  open  pet- 
cock  as  the  engine  is  turned  in  the  proper  direction  of  rotation  the  cylinder 
on  compression  can  be  determined.  The  breaker  contact  points  should 
just  be  starting  to  separate  (the  flywheel  being  turned  in  the  direction  of 
rotation  past  dead  center  position)  for  a  six-cylinder  engine,  or  from  1  in. 
to  1%  in.  (as  measured  on  the  flywheel)  past  dead  center  for  a  four- 
cylinder  engine. 

If  it  is  found  necessary  to  readjust  the  timing,  the  distributor  arm 
(which  has  an  arrow  on  it)  should  be  removed  and  the  nut  which 
holds  the  cam  in  place  unscrewed.  The  cam  can  be  loosened  by  giving 
it  a  sharp  rap  to  release  it  from  the  taper  part  of  the  shaft  on  which  it 
fits  snugly.  It  should  be  turned  to  obtain  the  proper  time  of  opening 
the  contact  points,  noting  that  it  strikes  the  fiber  in  the  proper  direction 
of  rotation.  The  cam  is  then  rapped  down  in  place  'and  the  nut  tight- 
ened to  keep  the  cam  from  slipping. 

Oiling. — The  grease  cup  below  the  distributor  head  should  be  kept 
full  of  medium  grease,  and  should  be  given  two  turns  to  the  right  every 
500  miles,  so  as  to  force  a  little  grease  into  the  bearings. 

Spark  Plugs. — Failure  of  spark  is  sometimes  due  to  the  spark  plug 
gap  inside  the  cylinder  becoming  clogged  with  carbon  or  oil.  This  gap 
should  measure  .025  in.  to  .030  in.,  or  the  thickness  of  the  gage  supplied 
by  the  manufacturer. 

75.  The  Remy-Liberty  Ignition  Breaker  for  U.  S.  Military  Truck, 
Class  B. — The  special  battery  ignition  breaker  manufactured  by  the  Remy 
Electric  Company  for  the  U.  S.  military  truck,  Class  B,  is  shown  in  Fig. 
125  and  Fig.  126.     The  breaker  is  of  the  closed  circuit  type  and  operates 
with  a  plain  non-vibrating  coil.     Both  breaker  and  coil  are  mounted  on 
the  left  side  of  the  engine  in  front  of  the  water  pump.     The  coil  is  de- 
signed so  that  a  resistance  unit  is  not  used  in  the  primary  circuit.     The 
condenser  is  mounted  inside  the  distributor  head  where  it  is  very  accessible. 
Another  feature  is  that  the  breaker  mechanism  is  mounted  on  a  plate 
separate  from  the  main  distributor  body.     This  permits  the  advancing 
and  retarding  of  the  spark  by  simply  shifting  the  breaker  mechanism 
around  the  cam  instead  of  shifting  the  entire  head,  thus  avoiding  the 
bending  of  the  wiring.     The  operation  and  adjustment  of  the  system  are 
identical  with  other  systems  of  the  closed  circuit  type. 

76.  The  North  East  Battery  Ignition  System. — The  installation  and 
wiring  of  the  North  East  battery  ignition  system  as  used  on  the  Dodge  car 
is  shown  in  Fig.  89.     The  ignition  unit,  Fig.  127,  is  virtually  a  magneto 


MODERN  BATTERY  IGNITION  SYSTEMS 


99 


replacement  outfit,  being  driven  the  same  as  a  magneto.  This  unit  com- 
prises an  induction  coil,  a  breaker  of  the  closed  circuit  type,  a  condenser 
mounted  in  the  breaker  housing,  and  an  automatic  spark  advance  mech- 


FIG.  125. — Remy-Liberty   battery   ignition   unit   for   U.    S.    Military   truck,   Class   B. 


CONDENSER 


TIMING  ADJUSTING  SCREW 


CAM 


PLATE  CARRYING 
BREAKER  nECHANlSH 


BEAKER  POINTS 
(ADJ.WOPENQ.On 
700.022  OfAMNCf 


TERMINAL  CONNECTED 
TO  COIL 


'DISTRIBUTOR  ARM      ^DISTRIBUTOR 


FIG.  126. — Construction  of  Remy-Liberty  battery  ignition  unit  for  U.  S.  Military  truck. 

Class  B. 

anism  which  is  shown  separately  in  Fig.  128.  Either  one  of  two  types 
of  breaker  is  used.  In  one  type,  the  terminals  of  the  breaker  are  both 
insulated  and  the  system  operates  with  a  polarity  changing  type  switch. 


100 


AUTOMOTIVE  IGNITION  SYSTEMS 


In  the  other  type,  Fig.  129,  one  breaker  terminal  is  grounded  and  the 
system  operates  with  a  simple  key  switch. 


TERtllNAL  CONNECTION 
TO  SWITCH  ON 


INDUCTION- 
COIL 


.HIGH  TENSION' 
LEAQ    FROM 
INDUCTION  COIL 
TO  DISTRIBUTOR 


DISTRIBUTOR 


L|  -  BREAKER  HOUSING 


HOUSING  CONTAINING 
AUTOMATIC  SPARK 
ADVANCE  MECHANISM 


FIG.   127. — North  East  ignition  unit. 


GOVERNOR 
SPRINGS 


GOVERNOR  WEIGHTS 


.DRIVING  SHAFT 
Y 


SPIRAL  GEAR  DRIVE 
TO  TJMER  SHAFT 


FIG.   128. — North  East  automatic  spark  advance  mechanism. 


INSULATED 
T£Rt11NAL\ 


T/tf£  ADJUST/NO 
NUT 


HIGH  TENSION 
TERMINAL  CONN. 
TO  INDUCTION  COIL 


CAM      DISTRIBUTOR 
CONTACT  POINTS 


BREAKER 


FIG.   129. — North  East  breaker  and  distributor. 

The  principle  of  the  system,  as  well  as  the  method  of  ignition  timing, 
is  very  similar  to  that  in  other  systems  of  the  closed  circuit  type.  To 
time  ignition  the  cam  is  loosened  and  the  time  of  contact  break  is  adjusted 
by  shifting  the  cam  so  that  the  points  are  on  the  verge  of  separating  when 


MODERN  BATTERY  IGNITjflX        S&W&%  \  /;       101 

the  cam  is  being  turned  forward  with  No.  1  piston  about  %  in.  below  upper 
dead  center  position  on  the  working  stroke. 

A  good  way  to  check  the  time  of  contact  break  is  with  a  test  lamp, 
connected  as  shown  in  Fig.  130.  After  the  ignition  switch  is  turned 
on,  the  engine  should  be  turned  over  slowly  by  hand.  The  light  will 
flash  on  and  off  depending  upon  whether  the  contacts  are  open  or  closed. 
The  instant  the  points  separate,  the  lamp  will  light.  The  light  should 
occur  (with  the  above  setting)  when  the  dead  center  mark  on  the  fly- 
wheel is  ^  m-  to  %  in.  past  dead  center  position.  The  time  of  con- 
tact opening  should  be  the  same  for  each  cylinder.  The  points  should 
be  adjusted  to  separate  .020  in. 

77.  The  Delco  Ignition  System. — A  few  of  the  many  types  of  Delco 
ignition  equipment  in  use  are  shown  in  Fig.  131  and  Fig.  132.  The 
varied  designs  are  due  not  so  much  to  the  principle  involved,  as  this 
is  practically  the  .same  in  all  models,  but  to  the  many  individual  igni- 


DISTRIBUTOR  BRUSH 


TO  SWITCH 
AND  BATTERY 


£Sr  LAMP 


THIS  TERfltNAt' 
GROUNDED 


/ 

CONTACTS  SHOULD  OPEN  0.020" 


FIG.   130. — Method  of  connecting  test  lamp  to  check  time  of  contact  opening. 

tion  requirements  of  the  four-,  six-,  eight-,  or  twelve-cylinder  engine 
on  which  they  are  used. 

The  distributor  and  breaker  unit  are  carried  on  the  front  end  of  the 
generator  and  are  driven  at  one-half  crankshaft  speed  by  the  same 
shaft  which  drives  the  generator.  The  distributor  consists  of  a  cap 
or  head  of  insulating  material  with  one  high-tension  contact  in  the 
center  and  as  many  similar  contacts  as  there  are  cylinders  spaced  equi- 
distant about  the  center.  The  distributor  arm  or  rotor  carries  a  con- 
tact button  which  makes  continuous  contact  with  the  head  and  serves 
to  direct  the  secondary  current  to  the  proper  spark  plug. 

Beneath  the  distributor  head  and  the  rotor  is  the  breaker,  Fig.  133, 
which  is  provided  with  a  screw  in  the  center  of  the  shaft.  The  loosen- 
ing of  this  screw  allows  the  cam  to  be  turned  in  either  direction  to  se- 
cure the  proper  timing.  The  breaker  operates  on  the  closed  circuit 
principle,  and  the  spark  occurs  at  the  instant  the  timer  contacts  open. 
The  adjustment  screw  must  always  be  screwed  down  tight  after  the 
cam  is  adjusted. 

The  distributor  is  equipped  with  both  manual  and  automatic  con- 


102  AU'VOMOTtVB  "IGNITION  SYSTEMS 


OLDSMOBILE. 


AUSTIN. 


PATTERSON. 


PACKARD.  CADILLAC.  NATIONAL. 

FIG.   131. — Types  of  Delco  ignition  equipment. 


FIG.  132. — Typical  1920  Delco  ignition  type  generators. 


MODERN  BATTERY  IGNITION  SYSTEMS 


103 


trol.  The  manual  control  is  linked  up  with  the  spark  lever  on  the 
steering  wheel  sector.  This  is  for  the  purpose  of  securing  the  proper 
retard  of  the  ignition  for  the  starting  operation  and  very  slow  idling 
speeds,  and  to  secure  the  proper  advance  required  for  maximum  power 
at  very  low  engine  speeds  over  which  the  automatic  feature  has  no 
control. 

The  automatic  spark  advance  mechanism  is  located  in  the  lower 
part  of  the  breaker  housing.  This  mechanism  is  for  the  purpose  of 
securing  the  additional  advance  that  is  required  to  give  the  best  operat- 
ing conditions  of  the  engine  at  the  higher  engine  speeds.  This  feature 
makes  it  unnecessary  to  manipulate  the  spark  lever  for  varying  engine 
speeds  in  order  to  secure  the  best  performance  of  the  engine. 


DIMMING 
RESISTANCE 


TO     SPARK   PLUGS 


BREAKER 

(CONTACTS  SHOULD 
OPEN    018" TO  OZO- 


MAMUAl   ADVANCE 
AND  RETARD  LEVER 


FIG.   133. — Wiring  diagram  for  typical  Delco  ignition  system. 

The  ignition  coil  is  mounted  on  top  of  the  generator  as  shown  in 
Fig.  132.  It  will  be  noticed  from  Fig.  133  that  an  ignition  resistance 
unit  is  mounted  on  one  end  and  that  the  condenser  is  placed  in  the  bot- 
>tom  of  the  coil  with  one  side  grounded.  The  switch  button  next  to 
the  ammeter,  Fig.  131  and  Fig.  132,  controls  both  the  ignition  circuit 
and  the  circuit  between  the  generator  and  the  storage  battery.  It 
connects  the  three  contacts  numbered  2,  4,,  and  3  in  the  wiring 
diagram,  Fig.  133.  The  second  button  from  the  ammeter  controls 
the  cowl  and  tail  light;  the  third  button  controls  the  headlight  dim; 
and  the  button  on  the  extreme  left  controls  the  headlight  bright. 

78.  The  Westinghouse  Ignition  Systems.  — The  Westinghouse 
Vertical  Ignition  System  is  characterized  mainly  by  the  fact 
that  the  interrupter,  condenser,  distributor,  and  induction  coil  are  all 
contained  in  a  single  unit  known  as  the  Westinghouse  Vertical  Igni- 


104 


AUTOMOTIVE  IGNITION  SYSTEMS 


tion  Unit.     This  ignition  unit  is  sometimes  mounted  independently, 
but  it  is  generally  mounted  on  the  generator  as  shown  in  Fig.  134. 

The  construction  of  the  unit  is  clearly  shown  in  Fig.  135  which 
shows  the  interrupter  at  the  bottom  of  the  assembly  with  the  condenser 
connected  directly  across  the  contact  points.  This  close  association 
of  the  contact  points  and  the  condenser  gives  a  more  positive  condenser 


FIG.  134. — Westinghouse  vertical  ignition  unit  mounted  on  an  automobile  engine. 

action  and  a  better  operation  of  the  ignition  system  than  when  the 
contact  points  and  the  condenser  are  widely  separated.  Immedi- 
ately above  the  interrupter  is  the  induction  coil  containing  the  prim- 
ary and  secondary  windings.  At  the  top  of  the  unit  is  the  distributor. 
The  distributor  arm  is  driven  by  a  shaft  which  extends  upward  from 


CVS TRi BUt OB.  PLATE 


FIG.   135. — Parts  of  Westinghouse  vertical  ignition  unit. 

the  interrupter  through  the  hollow  core  of  the  induction  coil.  This 
arrangement  gives  a  very  compact  ignition  system  as  most  of  the  re- 
quired parts  are  located  in  one  unit.  The  only  parts  of  the  circuit 
that  are  outside  of  this  unit  are  the  battery,  ignition  switch,  and  bal- 
last resistor.  The  ballast  resistor  is  mounted  on  the  back  of  the  igni- 
tion switch,  Fig.  136  and  Fig.  137.  The  ignition  switch  is  double  pole 


MODERN  BATTERY  IGNITION  SYSTEMS 


105 


and  is  so  arranged  that  the  current  passes  through  the  breaker  points 
in  a  different  direction  every  time  the  switch  is  turned  on.     This  re- 


FIG.  136. — Front  view,  Westing- 
house  ignition  switch. 


FIG.  137. — Rear  view,  Westinghouse 
ignition  switch  with  resistor  ballast 
mounted  in  place. 


1^  To  SparH  Plugs 
Distributer  Brushes 

•Induction  Coil 
Interrupter  Contacts 


To  Ignition  Unit 


versal  of  current  through  the  breaker  points  prevents  them  from  pit- 
ting away  unevenly  and  lengthens  their  life. 

The  ballast  resistor,  which  is  an  integral  part  of  the  primary  cir- 
cuit, consists  of  a  resistance  unit  having 
a  high  temperature  coefficient.  It  is 
placed  in  series  with  the  primary  of 
the  induction  coil  and  all  current  flow- 
ing through  the  primary  circuit  must 
pass  through  this  resistor.  If  the 
ignition  switch  should  be  left  on  with 
the  engine  idle,  the  uninterrupted 
current  would  heat  the  resistor,  thus 
increasing  its  resistance  and  cutting 
down  the  amount  of  current  to  such 
a  low  value  that  the  coil  would  not 
be  burned  out. 

When  the  engine  is  running,  a 
certain  amount  of  current  will  flow 
through  the  primary  circuit  at  each 
closing  of  the  contacts.  With  an  in- 
crease in  engine  speed,  the  time  of  con- 
tact is  shortened  and  the  time  allowed 
the  primary  current  to  build  up  is 
materially  reduced.  As  the  period  of 
current  flow  is  reduced  in  length,  the 
resistor  cools,  its  resistance  is  lowered, 
and  the  value  of  the  current  in  amperes 
that  passes  is  increased,  allowing  the  current  in  the  primary  coil  to  build 
up  very  rapidly.  Under  this  regulation,  a  small  current  is  produced 
in  the  primary  circuit  at  low  engine  speeds,  and  a  large  current  at  high 
engine  speeds,  while  the  magnitude  of  the  spark  produced  by  the  sec- 


Battery 


From  Battery 

FIG.   138. — Wiring  diagram  for  Westing- 
Chouse  vertical  ignition  system. 


106 


AUTOMOTIVE  IGNITION  SYSTEMS 


ondary  winding  is  uniform  at  all  engine  speeds.     The  wiring  diagram 
of  the  vertical  unit  ignition  system  is  shown  in  Fig.  138. 


A 


FIG.   139. — Westinghouse  type 
SC  ignition  coil. 


FIG.   140. — Westinghouse  type  SC  dis- 
tributor for  an  eight-cylinder  engine. 


The  Westinghouse  Type  SC  Ignition  System. — A  later  model  Westing- 
house  ignition  system  is  the  type  SC  which  uses  a  coil  separate  from  the 


Fibre  Retaining 
Piece 


Terminal 


Distributor  Block 


Condenser 


^Movable 
1  Contact 


|  Stationary  Contact 


Oil  Hole 
Cover 


Distributor  Brush 


Cam 


FIG.  141.— Interior  of  Westinghouse  Type  SC  interrupter. 

distributor  unit.     This  coil,  shown  in  Fig.  139,  is  tubular  in  shape  and  is 
mounted  upon  a  metal  base  plate  which  facilitates  its  installation  at 


MODERN  BATTERY  IGNITION  SYSTEMS 


107 


any  convenient  place  either  on  the  engine  or  on  the  dash.  The  ballast 
resistor  is  carried  in  a  groove  around  the  porcelain  cap  instead  of  being 
mounted  on  the  ignition  switch  as  in  the  Vertical  Unit. 

The  distributor  unit  for  an  eight-cylinder  engine  is  shown  in  Fig.  140. 
The  distributor  unit  carries  but  one  low-tension  binding  post  since  the 
low-tension  current  is  grounded  in  the  interrupter.  Figure  141  shows 
the  interior  construction  of  the  interrupter.  The  movable  contact  point 
is  mounted  upon  a  steel  spring  which  flexes  under  the  action  of  the  inter- 
rupter cam,  thus  opening  the  circuit  at  the  contact  points.  The  con- 
denser is  contained  in  the  interrupter  housing  and  is  in  electrical  contact 
with  the  moving  contact  point.  The  stationary  contact  is  grounded 
directly  to  the  metal  housing  as  is  also  one  terminal  of  the  condenser. 
This  puts  the  condenser  in  parallel  with  the  breaker  points. 


CAM 


CONDENSER 


BALLAST  COIL 


SWITCH 


INTERRUPTER 

TO    SPARK    PLUGS 


CO|L  DISTRIBUTOR 

-.- 

FIG.  142. — Wiring  diagram,  Westinghouse  type  SC  ignition  system. 

The  wiring  diagram  of  the  type  SC  system  is  shown  in  Fig.  142. 
The  primary  winding  of  the  coil  has  two  terminals  located  on  the  top  of 
the  coil,  and  the  secondary  winding  has  one  terminal  on  the  side,  the  other 
end  of  the  secondary  winding  being  grounded  on  the  base  plate  of  the 
coil.  If  this  coil  be  mounted  on  an  insulating  support,  such  as  the  wooden 
dash  of  an  automobile,  a  wire  should  be  run  from  one  of  the  screws  or 
bolts  holding  the  coil  in  place  to  some  convenient  nut  or  bolt  on  the  metal 
work  of  the  engine.  A  simple  two-point  switch  is  used  for  the  ignition 
control. 

79.  The  Philbrin  Ignition  System. — The  Philbrin  ignition  system 
provides  a  combination  of  the  single  spark  and  the  high  frequency  vibrat- 
ing coil  continuous  spark  systems.  This  combination  is  effected  by  a 


108 


AUTOMOTIVE  IGNITION  SYSTEMS 


special  type  switch.  With  the  Philbrin  system  the  driver  has  the  option 
of  using  a  single  spark  system,  especially  adapted  for  driving  at  ordinary 
touring  speed  after  the  motor  has  been  warmed  up;  or  a  high  frequency 

SPARK  PLUG 


To  PLUG 


GROUND 


GROUND 


KEY  To  PHILBRIN  DUPLEX 
SELECTIVE  SWITCH 


I] 


CONTACT    MAKER 
AND  INTERRUPTER 


BATTERY 
GROUND 


POSITION    Or 
COMMUTATOR  BRUSHES 
WHEN  HIGH  FREQUENCY 
SYSTEM  fs  IN  OPERATION 

POSITION  OF 
COMMUTATOR  BRUSHES 
WHEN  SINGLE  SPARK 

OPERATION 


BATTERY     DUPLEX  SWITCH 
FIG.  143. — Wiring  diagram,  Philbrin  Duplex  ignition  sytem. 


FIG.   144. — Philbrin  distributor. 


spark  system  adapted  for  slow  driving  through  crowded  traffic  or  when 
the  engine  is  cold. 

That  a  clear  understanding  of  the  operation  may  be  had,  the  high 
frequency    system,   the   one   to  be   used   for  starting  a  cold  motor  in 


MODERN  BATTERY  IGNITION  SYSTEMS 


109 


winter,  will  be  considered  first.  Figure  143  is  the  wiring  diagram  of  the 
Philbrin  ignition  system.  With  the  selective  switch  in  the  position 
shown  by  the  heavy  solid  lines  the  path  of  the  current  through  the  circuit 
is  as  follows:  From  battery  to  primary  winding  on  coil,  to  selective 


FIG.   145. — Interior  of  Philbrin  Duplex  switch. 

switch,  to  vibrating  coil  winding  through  vibrating  points,  to  ground. 
The  contact  maker  or  interrupter  is  not  included  in  this  circuit;  conse- 
quently, the  vibrator  is  working  continuously,  producing  a  steady  stream 


CONTACT 
POINTS 


FIG.   146. — Philbrin'contact  maker. 


of  sparks  in  the  secondary  circuit.  This  stream  of  sparks  is  distributed 
to  the  proper  cylinder  by  the  distributor,  Fig.  144.  In  this  case,  the 
distributor  acts  as  a  timer  for  the  high-tension  circuit.  The  continuous 
stream  of  high  frequency  sparks  produced  under  this  operation  permits 


110 


AUTOMOTIVE  IGNITION  SYSTEMS 


FIG.   147. — Philbrin  distributor  and  contact  maker  for  an         FIG.        148. — Philbrin 
eight-cylinder  engine.  waterproof  coil. 


FIG.  149. — Philbrin  distributor  unit  for  twelve-cylinder  engine,  with  coil  mounted 

on  base. 


MODERN  BATTERY  IGNITION  SYSTEMS 


111 


a  cold  motor  to  be  started  easily,  or  allows  the  driver  to  throttle  down 
the  engine  and  drive  slowly  in  crowded  traffic. 

Figure  145  shows  the  interior  construction  of  the  switch  used  by 
Philbrin.  It  carries  a  high  frequency  vibrator  with  a  condenser  con- 
nected across  its  points. 

By  turning  the  selective  switch  to  the  position  shown  by  the  dotted 
lines  in  Fig.  143,  the  system  will  operate  on  a  single  spark.  The  high 
frequency  vibrator  is  now  cut  out  of  the  circuit  and  the  contact  maker  or 
interrupter,  Fig.  146,  is  introduced  in  its  place.  The  contact  maker  is  of 
special  form,  designed  to  give  a  very  short  closed  circuit  period  with  a 
quick  break,  and  carries  a  condenser  connected  across  the  points.  On 
single  spark  operation,  the  system  gives  but  a  single  spark  in  each  cylinder 


FIG.  149a. — Wagner  ignition  system  mounted  on  generator. 

at  the  proper  firing  time.  The  assembled  contact  maker  and  distributor 
for  an  eight-cylinder  motor  is  shown  by  Fig.  147.  The  coil,  Fig.  148,  is 
of  special  waterproof  construction,  and  is  usually  mounted  on  the  under- 
hood  side  of  the  dash,  but  for  some  installations  the  coil,  contact  maker, 
and  distributor  are  grouped  into  a  compact  unit  as  shown  in  Fig.  149. 
80.  Wagner  Ignition  System. — The  Wagner  ignition  system  employs 
a  single  non-vibrating  coil  with  a  high-tension  distributor.  The  system 
is  usually  mounted  on  the  generator,  as  shown  in  Fig.  149a,  but  may  also 
be  mounted  independently  if  desired.  The  units  which  compose  the 
Wagner  system  have  been  designed  so  as  to  be  water  and  dust  proof, 
removing  many  causes  of  ignition  trouble  and  making  the  operation  of 
the  system  more  reliable. 

The  coil  shown  in  Fig.  1496  is  contained  in  a  pressed  steel  case  which 


112 


AUTOMOTIVE  IGNITION  SYSTEMS 


protects  the  parts  of  the  coil  from  mechanical  injury  and  moisture.     A 
resistance  unit  is  mounted  on  one  of  the  primary  terminals  near  the  hot- 


SAFETY  GAP 

•WITH 
fHCft  WINDOWS,, 


10W  TfNSlON 
TERMINAL 

TO  Bi   CONNfCTCD 
TO  SWIT 


FIG.   1496. —  Wagner  coil. 

torn  of  the  coil.     The  high-tension  terminal  is  at  the  extreme  top  of  the 
unit.     Immediately  below  is  the  safety  gap  placed  inside  the  case  with  a 


TIMER  LfVfff 


FIG.  149c. — Wagner  condenser. 


FIG.   149d. — Wagner  timer  or  interrupter. 


mica  window  through  which  it  may  be  seen.  The  condenser,  Fig.  149c, 
is  contained  in  a  pressed  steel  case.  This  construction  and  method  of 
assembly  protect  the  condenser  from  moisture,  temperature  changes,  or 


MODERN  BATTERY  IQNITION  SYSTEMS 


113 


mechanical  vibrations.     The  condenser  may  be  mounted  either  on  the 
distributor  housing  or  on  the  base  of  the  coil. 

The  timer  or  interrupter,  Fig.  149d,  is  carried  immediately  beneath  the 
high-tension  distributor  in  the  distributor  unit  shown  in  Fig.  149e.  The 
distributor  disc,  Fig.  149/,  distributes  the  high-tension  current  to  the 
various  spark  plug  cables  by  means  of  the  plate  D.  The  plate  does  not 
make  actual  contact  with  the  distributing  pins  shown  in  Fig.  1490,  but 
passes  very  close  to  them  with  about  one  ten-thousandths  of  an  inch  of 


FIG.  149e. — Complete  Wagner  timer  distributor. 

air  gap  across  which  the  current  jumps.  This  avoids  the  use  of  carbon 
brushes  and  does  away  with  cleaning  the  distributor  head. 

The  interrupter,  Fig.  149d,  provides  means  for  adjusting  the  contact 
points.  One  point  is  mounted  on  the  end  of  an  adjustable  contact-  screw 
held  in  place  by  the  lock  nut  H.  After  the  points  have  worn  until  they  no 
longer  give  the  proper  opening,  which  should  be  about  0.020  in.,  the  lock 
nut  may  be  loosened  and  the  contact  screw  turned  up  until  the  opening 
is  again  correct.  The  lock  nut  should  then  be  tightened. 

After  continued  use  for  a  long  period  the  contact  points  may  need 
replacing.  A  new  timer  lever  and  contact  screw  will  then  be  required. 


114 


AUTOMOTIVE  IGNITION  SYSTEMS 


The  old  timer  lever  and  contact  screw  should  be  removed  and  the  new 
parts  placed  in  position.  The  opening  of  the  contact  points  should  then 
be  adjusted  to  the  proper  distance  and  the  lock  nut  tightened.  The 
points  should  face  each  other  squarely  and  should  touch  throughout 
their  whole  surface  C,  Fig.  149dL  If  they  do  not  line  up,  the  screws  E 


FIG.  149/.— Wagner 
distributor  disc. 


FIG.   1490. — Wagner  distributing  head. 


and  F  should  be  loosened  and  the  support  plate  G  moved  sufficiently  to 
align  the  points  properly,  after  which  E  and  F  should  be  tightened. 

The  timer  lever  pivot  is  lubricated  by  an  oil-soaked  wick  contained 
in  the  hollow  spindle  under  the  spring  clip  A,  Fig.  149d.  At  the  beginning 
of  the  season  this  wick  should  be  given  about  three  drops  of  thin  oil  to 


FIG.  149&. — Timing  the  Wagner  interrupter. 

provide  lubrication  for  the  season.  The  grease  cup  on  the  distributor 
shaft,  Fig.  149e,  should  be  filled  with  grease  and  screwed  down  one-half 
turn  every  500  miles. 

If  the  setting  of  the  interrupter  has  been  disturbed  and  it  is  desired 
to  reset  it,  the  cam  screw  should  first  be  loosened  and  the  cam  raised  off 


MODERN  BATTERY  IGNITION  SYSTEMS 


115 


PARK       PLUOS 


INTERRUPTER 


its  taper  on  the  shaft  by  prying  it  up  with  a  screwdriver  as  shown  in  Fig. 
149/i.  Cylinder  No.  1  should  then  be  set  on  top  dead  center  of  the  work- 
ing stroke  and  the  spark  lever  retarded  to  the  limit  of  its  travel.  The 
cam  then  should  be  rested  lightly  on  the  taper  of  the  shaft  and  turned 
around  in  the  direction  in  which  it  rotates  when  driven  by  the  engine 
until  the  slot  B  is  opposite  the  cam  on  the  timer  lever  C,  with  the  points 
just  opening.  The  top  of  the  cam  should  then  be  tapped  lightly  with  the 
handle  of  the  screwdriver  to  force  it  solidly  on  to  the  tapered  portion  of 
the  shaft  and  the  cam  screw  tightened.  The  opening  of  the  contact 
points  should  be  again  checked  with  the  position  of  the  piston  to  insure 
that  the  adjustments  have  not  been  disturbed  when  the  cam  was 
tightened.  The  wiring  diagram  is  shown  in  Fig. 

80a.  Timing  Battery  Igni- 
tion with  the  Engine. — The 
details  connected  with  igni- 
tion timing  depend  somewhat 
on  the  make  and  type  of  igni- 
tion system  and  also  on  the 
type  of  engine.  The  general 
principles,  however,  are  the 
same.  The  following  rules  for 
timing  a  four-cylinder  engine, 
with  minor  modifications  to 
suit  certain  individual  condi- 
tions, will  apply  generally  to  all  systems  of  the  closed-circuit  type  hav- 
ing an  adjustable  interrupter  cam. 

Place  the  spark  lever  on  the  steering  wheel  in  the  fully  retarded  posi- 
tion, making  sure  that  the  interrupter  timer  lever  is  fully  retarded  and 
that  all  play  in  the  connecting  mechanism  from  spark  lever  to  timer  has 
been  taken  up. 

With  the  pet  cocks  open  or  the  spark  plugs  removed,  turn  the  engine 
over  slowly  by  hand.  After  noting  the  firing  order,  either  by  testing  the 
order  of  compression  or  by  watching  the  operation  of  the  valves,  turn  the 
engine  until  the  dead-center  mark  on  the  flywheel  for  No.  1  and  4  cylin^ 
ders  (D.  C.  1-4)  is  about  1  in.  past  dead-center  position  with  No.  1 
cylinder  (the  cylinder  next  to  the  radiator)  on  the  upper  end  of  its  com- 
pression stroke.  (One  inch  measured  on  the  rim  of  a  16%  in.  flywheel 
measures  off  about  seven  degrees  of  the  crank  angle.)  In  a  four-cylinder 
engine,  the  exhaust  valve  in  No.  4  cylinder  should  just  be  closed  with 
this  setting. 

Remove  the  distributor  head  and  loosen  the  timing  adjusting  screw 
or  nut  in  the  center  of  the  timer  shaft.  Turn  the  breaker  cam  so  that  the 
distributor  brush  or  button  will  be  in  the  position  under  No.  1  high-tension 
terminal  when  the  distributor  head  is  fastened  in  the  proper  position. 


FIG.  149*. — Wiring  diagram,  Wagner 
ignition  system. 


116  AUTOMOTIVE  IGNITION  SYSTEMS 

In  this  position,  adjust  the  breaker  cam  carefully  so  that  when  the  dis- 
tributor arm  is  rocked  forward,  taking  up  the  slack  in  the  gears,  the  con- 
tacts will  be  opened  by  the  breaker  cam,  and,  when  the  arm  is  rocked 
backward,  the  contacts  will  close. 

Tighten  the  adjustment  screw  or  nut  securely  and  replace  the  dis- 
tributor arm  and  head.  The  head  should  be  properly  located  by  the 
locating  tongue  and  the  hold-down  clips.  The  distributor  should  be 
wired  to  the  plugs  in  the  proper  order  of  firing,  beginning  with  No.  1  and 
proceeding  around  the  distributor  head  in  the  direction  of  breaker  rotation. 

81.  Care  of  Battery  Ignition  Systems. — General  rules  which  will 
provide  proper  care  and  insure  long  life  to  practically  all  types  and  makes 
of  battery  ignition  systems  are  as  follows : 

Contact  Points  and  Distributor. — The  distributor  cap  should  be 
removed  and  the  contact  points  inspected  every  1000  to  1500  miles. 
If  found  dirty  or  uneven  and  pitted,  a  fine  flat  file,  or  preferably  a  piece 
of  No.  00  sandpaper,  should  be  passed  between  them.  The  contact 
points  have  a  standard  opening  of  .017  in.  to  .020  inch. 

The  Distributor. — The  distributor  cap  will  require  no  attention  except 
to  wipe  out  from  time  to  time  any  dust  which  may  accumulate.  This 
may  be  done  by  using  a  rag  moistened  with  gasoline. 

Oiling. — Each  bearing  of  the  breaker  distributor  unit  should  be  given 
a  few  drops  of  clean  cylinder  oil  every  1000  miles.  Oil  is  much  cheaper 
than  new  bearings. 

Every  1000  to  1500  miles  a  slight  trace  of  clean  oil  or  grease  placed  on 
the  fiber  block  or  on  the  steel  cam  will  keep  the  cam  from  rusting.  The 
contact  points  should  not  be  oiled. 

Wiring. — Once  or  twice  each  season  all  wiring,  especially  the  high- 
tension  cables,  should  be  thoroughly  inspected  and  all  wires  with  worn  or 
cracked  insulation  replaced  with  new.  All  terminals  should  be  kept 
tight.  Care  should  be  taken  that  each  secondary  wire  is  kept  free  from 
oil  and  well  supported  so  that  there  is  no  rubbing  contact  with  the  engine 
frame.  Short  circuits  and  misfiring  of  the  engine  are  thus  avoided. 

Spark  Plugs. — Failure  of  ignition  is  usually  due  to  dirty  spark  plugs. 
When  the  engine  does  not  fire  regularly,  the  plugs  should  be  examined, 
and,  if  found  to  be  sooted,  they  should  be  cleaned  by  scraping  off  the 
carbon  and  washing  them  in  gasoline.  The  opening  of  the  plug  gap 
should  measure  .025  in.  to  .030  in.,  or  the  thickness  of  a  worn  dime. 
After  the  plugs  have  been  replaced  in  the  cylinder,  the  procelains  should 
be  examined  to  be  sure  that  they  are  not  cracked. 


CHAPTER  V 


BATTERY  IGNITION  SYSTEMS  FOR  MULTIPLE   CYLINDER 

ENGINES 

82.  Firing  Order  of  Four-  and  Six-cylinder  Engines. — The  firing 
order  of  a  multiple  cylinder  engine  is  arranged  so  as  to  give  an  even  time 
distribution  of  power  impulses  along  the  crankshaft.  The  standard 
four-cylinder  crankshaft  has  the  two  center  cranks,  No.  2  and  No.  3,  side 
by  side.  The  end  cranks  No.  1  and  No.  4  are  at  an  angle  of  180°  from 
the  center  cranks  as  shown  in  Fig.  150.  This  arrangement  causes  the 
pistons  to  move  in  pairs,  No.  2  and  No.  3  forming  one  pair  and  No.  1  and 


Main 

bear/nog  -  ^ 


FIG.  150. — Four-cylinder  crankshaft. 

No.  4  the  other  pair.  When  the  center  pair  of  pistons  is  moving  up,  the 
end  pair  is  moving  down  and  vice  versa,  thus  giving  a  smooth  running 
motor  without  excessive  vibration.  The  No.  i  piston  and  the  No,  4 
piston  are  in  the  same  position  in  the  cylinders  at  the  same  time.  Like- 
wise, No.  2  and  No.  3  pistons  are  in  the  same  position.  If  No.  1  piston 
is  on  the  compression  stroke,  No.  4  must  necessarily  be  on  the  exhaust 
stroke,  and  No.  2  and  No.  3  on  the  suction  and  explosion  strokes.  On 
account  of  the  arrangement  of  the  cranks  on  the  shaft,  the  order  of  firing 
in  a  four-cylinder  engine  must  be  1,  3,  4,  2,  or  1,  2,  4,  3.  Either  of  these 
firing  orders  gives  an  even  distribution  of  the  power  impulses.  Ignition 
systems  to  be  used  on  four-cylinder  engines  must  have  their  timers,  con- 

117 


118 


AUTOMOTIVE  IGNITION  SYSTEMS 


tact  makers,  and  distributors  designed  to  deliver  the  spark  to  the  cylin- 
ders of  the  engine  in  one  of  these  firing  orders.  By  a  study  of  the  timer 
in  Fig.  83  and  the  distributor  in  Fig.  105,  it  can  readily  be  understood 
how  this  is  accomplished.  These  timers  and  distributors  are  driven  at 
one-half  crankshaft  speed. 

There  are  two  ways  in  which  cranks  on  a  six-cylinder  crankshaft  are 
arranged.  The  sketches  in  Fig.  151  show  this  essential  difference. 
Starting  with  crank  1  up,  as  shown,  crank  2  may  be  either  120°  to  the 
right  or  left.  Crank  3  is  then  120°  beyond  crank  2.  In  either  case,  cranks 
1  and  6,  2  and  5,  3  and  4  are  in  the  same  plane  and  in  the  same  position. 
A  crankshaft  is  either  right  or  Left,  depending  upon  whether  cranks  3  and  4 


3*4  2+5 

FIG.  151. — Methods  of  crank  arrangement  for  six-cylinder  engine. 

are  120°  to  the  right  or  left  of  cranks  1  and  6,  when  the  latter  are  vertical. 
Figure  151A  represents  a  right  crank  and  Fig.  151B  a  left  crank,  the  fly- 
wheel being  at  the  far  end  of  the  shaft.  As  each  cylinder  fires  once  in  two 
revloutions  of  the  crankshaft,  there  are,  consequently,  three  explosions 
per  revolution,  or  one  every  one-third  revolution  of  a  six-cylinder  crank. 
The  only  essential  difference  between  a  right  and  a  Left  crank  is  that  in 
one  case  the  flywheel  is  on  one  end  of  the  crankshaft,  while  in  the  Dther 
it  is  placed  on  the  opposite  end.  The  crank  arrangement  determines  the 
firing  order,  assuming  that  the  direction  of  rotation  is  the  same  in  each 
case.  Referring  to  Fig.  151,  obviously  pistons  1  and  6,  2  and  5,  and  3 
and  4,  will  be  in  the  same  respective  positions  in  their  cylinders  at  the 
same  time.  If  pistons  1,  2,  or  3  are  on  the  suction  stroke,  then  pistons  6, 


MULTIPLE  CYLINDER  IGNITION  SYSTEMS  119 

5,  or  4  will  be  on  the  expansion  stroke,  If  1,  2,  or  3  are  on  the  compres- 
sion stroke,  then  6,  5,  or  4  will  be  on  the  exhaust  stroke.  It  is  also  evident 
that  the  cylinders  can  fire  only  in  certain  definite  orders.  For  instance, 
the  right  crank  in  Fig.  15L4.  might  fire,  1,  5,  3,  6,  2,  4,  or  1,  2,  3,  6,  5,  4,  or 
1,  5,  4,  6,  2,  3,  or  1,  2,  4,  6,  5,  3.  The  first  order  given,  1,  5,  3,  6,  2,  4,  is 
the  best  and  most  usual  firing  order  because  the  power  impulses  are 
better  distributed  along  the  crankshaft.  The  left  crank,  Fig.  151#, 
might  fire  1,  3,  5,  6,'  4,  2,  or  1,  4,  5,  6,  3,  2,  or  1,  3,  2,  6,  4,  5,  or  1,  4,  2,  6, 
3,  5.  The  last  order,  1,  4,  2,  6,  3,  5,  is  the  best  ord.er  for  the  reason  given 
above. 

83.  Firing   Order   of   Eight-cylinder   Engines. — The   eight-cylinder 
automobile  engine  has  two  rows  or  " blocks"  of  four  cylinders  each  placed 


FIG.   152. — Sectional  view  of  Cadillac  eight-cylinder  engine. 

at  an  angle  of  90°  with  each  other  as  shown  in  Fig.  152.  The  crankshaft 
is  like  the  conventional  four-cylinder  crankshaft.  The  cylinders  in  the 
two  blocks  are  opposite,  and  the  connecting  rods  of  opposite  cylinders 
work  on  the  same  crank  as  shown  in  Fig.  153. 

The  cylinders  of  an  eight-cylinder  engine  are  generally  numbered  as 
shown  in  Fig.  154 A,  the  right  and  left  blocks  being  numbered  from  the 
radiator  to  the  rear.  The  possible  firing  orders  of  each  block  are  the 
same  as  in  a  four-cylinder  engine.  It  will  be  noticed  that  on  account  of 
the  cylinder  blocks  being  placed  at  an  angle  of  90°,  when  the  pistons  of 
cylinders  1L  and  4L  are  at  the  top  of  the  stroke,  pistons  2L  and  3L  are  at 
the  bottom  of  the  stroke  and  all  pistons  of  the  right  block  are  at  the  mid- 
dle of  the  stroke,  two  of  them  moving  towards  the  top  and  the  other  two 
towards  the  bottom.  This  means  that  the  power  impulses  will  be  90° 


120 


AUTOMOTIVE  IGNITION  SYSTEMS 


apart,  and  that  the  firing  will  alternate  from  one  side  to  the  other.  Al- 
though it  is  possible  to  have  four  firing  orders  for  an  eight-cylinder 
engine,  two  of  these  are  practically  never  used.  Both  cylinder  blocks  usu- 
ally fire  in  the  1,  3,  4,  2  order  or  the  1,  2,  4,  3  order.  If  in  the  1,  3,  4,  2 


FIG.  153. — Cadillac  crankshaft,  piston,  and  connecting  rod  assembly. 

order,  the  firing  order  for  the  engine  is  1L,  2R,  3L,  1R,  4L,  3R,  2L,  4R  as 
shown  in  Fig.  1544.  If  the  1,  2,  4,  3  order  is  used,  the  engine  fires  1L, 
3R,  2L,  1R,  4L,  2R,  3L,  4R  as  in  Fig.  1544. 


I  RADIATOR  RADIATOR    |         RADIATOR  f  I     RADIATOR    I 

LEFT RIGHT          LEFT  RIGHT          I  EFT  RIGHT          LEFT  RIGHT 


A  B  C  D 

FIG.   154. — Methods  of  numbering  the  cylinders  on  an  eight-cylinder  engine. 

The  system  of  numbering  the  cylinders  is  not  always  as  shown  in  Fig. 
154 A.  The  cylinders  may  be  numbered  in  the  order  of  firing  as  on  the 
Cadillac,  Fig.  154.B,  or  as  on  the  Cole  car,  Fig.  154C,  where  the  cylinders 
are  numbered  1,  2,  3,  4,  on  the  right  side,  beginning  at  the  radiator,  and 
5,  6,  7,  8  on  the  left  side,  also  beginning  at  the  radiator.  The  order  of 


MULTIPLE  CYLINDER  IGNITION  SYSTEMS  121 

firing  on  the  Cadillac  corresponds  to  the  order  previously  given,  1L,  2R, 
3L,  1R,  4L,  3R,  2L,  4R.  The  firing  order  on  the  Cole  is  1,  8,  3,  6,  4,  5,  2,  7, 
as  in  Fig.  154C,  which  is  the  same  order  as  on  the  Cadillac.  The  number- 
ing and  order  of  firing  on  the  Oldsmobile  and  King  Eight  are  the  same 
as  on  the  Cole  car,  Fig.  154(7. 

84.  Determining  the  Firing  Order  of  an  Eight-cylinder  Engine. — If 
it  becomes  necessary  to  determine  the  firing  order  of  an  eight-cylinder 
engine  it  can  be  easily  done  by  assuming  that  the  cylinders  are  numbered 
as  indicated  in  Fig.  154D.     The  firing  order  for  the  right  block  is  deter- 
mined by  cranking  the  engine  so  that  cylinder  No.  1  is  on  compression. 
By  further  cranking,  it  can  be  determined  whether  cylinder  No.  2  or 
cylinder  No.  3  is  next  on  compression.     If  No.  1  is  followed  by  No.  2,  the 
firing  order  for  the  block  will  be  1,  2,  4,  3;  if  No.  1  is  followed  by  No.  3, 
the  order  will  be  1,  3,  4,  2.     The  firing  order  for  the  engine  can  then  be 
determined  by  starting  with  right  cylinder  No.  1,  following  this  with  left 
cylinder  No.  1,  and  then  by  R2,  L2,  R4,  L4,  R3,  L3  if  the  firing  order  of 
the  block  is  1,  2,  4,  3.     If  the  firing  order  of  the  block  is  1,  3,  4,  2,  then 
the  order  for  the  engine  will  be  Rl,  LI,  R3,  L3,  R4,  L4,  R2,  L2. 

If  the  distributor  and  the  ignition  system  have  been  installed,  the 
easiest  way  to  determine  the  firing  order  of  any  engine  is  to  note  the 
direction  of  rotation  of  the  distributor  arm.  The  cable  from  the  spark 
plug  in  cylinder  No.  1  on  the  right  block,  or  the  front  cylinder  if  the  en- 
gine has  but  one  block,  is  followed  to  the  distributor  and  the  distributor 
terminal  to  which  it  is  attached  noted.  By  noting  to  which  cylinders  the 
successive  cables  lead,  when  going  around  the  distributor  in  the  direction  of 
rotation  of  the  distributor  arm,  the  firing  order  can  readily  be  determined. 
This  method  is  the  better  when  the  ignition  system  is  already  installed ; 
if  this  is  not  the  case,  the  first  method  must  be  used. 

85.  The  Delco  Ignition  System  for  the  Oldsmobile  Eight. — A  typical 
eight-cylinder  ignition  system  is  the  Delco  ignition  equipment  as  in- 
stalled on  the  Model  45A  Oldsmobile  Eight.     The  ignition  unit,  con- 
sisting  of  the  interrupter  and  an  eight-point  distributor,  is  mounted 
vertically  on  the  commutator  end  of  the  electrical  generator,  Fig.  155. 
The  generator  in  turn  is  mounted  between  the  cylinder  blocks  at  the 
front  end  of  the  engine  as  shown  in  Fig.  156.     The  ignition  unit,  although 
mounted  on  the  generator  which  is  driven  by  the  fan  belt,  is  not  driven 
from  the  generator  shaft  but  has  an  independent  drive  consisting  of  a 
vertical  shaft  with  a  spiral  gear  which  meshes  with  a  gear  on  the  camshaft. 

In  the  lower  part  of  the  ignition  unit  case  is  located  the  automatic  spark 
advance  mechanism  of  the  conventional  centrifugal  weight  governor 
type.  Immediately  above  is  the  breaker  and  at  the  top  the  distributor 
covered  by  its  hard  rubber  cap.  The  condenser  is  located  within  the 
breaker  housing  in  close  association  with  the  breaker  points.  The  cam 
operating  the  breaker  has  eight  lobes  so  as  to  give  eight  sparks  per  revolu- 


122 


AUTOMOTIVE  IGNITION  SYSTEMS 


tion  of  the  cam,  the  ignition  unit  being  driven  at  one-half  crankshaft 
speed. 

The  coil  used  is  of  the  regular  Delco  tubular  three-terminal  form  with 
the  resistance  unit  carried  at  one  of  the  primary  terminals.  The  coil  is 
mounted  on  a  bracket  secured  to  the  engine  side  of  the  dash.  The  wiring 


FIG.   155. — Delco  generator  and  ignition  unit  for  Oldsmobile  Eight. 

diagram  of  the  electrical  equipment  on  the  Oldsmobile  Model  45A  is 
shown  in  Fig.  157.  The  different  parts  of  the  electrical  equipment 
are  shown  here  in  their  relative  positions,  and,  consequently,  the  parts 
described  can  be  readily  located. 


FIG.   156. — Delco    ignition  installation  on  Oldsmobile  eight-cylinder  engine,  model  45A. 

86.  The  Delco  Ignition  System  for  the  Cadillac  Eight. — This  ignition 
system  embodies  the  following  elements:  A  source  of  current,  the  gen- 
erator, or  at  low  engine  speeds,  the  storage  battery;  an  ignition  timer  or 
interrupter,  which  interrupts  the  low-tension  current  at  the  proper  instant 


MULTIPLE  CYLINDER  IGNITION  SYSTEMS 


123 


124 


AUTOMOTIVE  IGNITION  SYSTEMS 


to  produce  a  spark  in  the  high-tension  circuit;  an  induction  coil,  transform- 
ing the  primary  current  of  six  volts  into  one  of  sufficient  voltage  to  jump 
the  gaps  in  the  spark  plugs;  a  condenser,  which  assists  the  inductance 
coil  to  raise  the  voltage,  and  which  protects  the  contact  points  of  the 
breaker  from  burning;  and  a  high-tension  distributor,  which  directs  the 
distribution  of  the  high-tension  current  to  the  spark  plugs  in  the  respec- 
tive cylinders.  These  various  parts  are  shown  in  Fig.  158.  The  combina- 
tion switch,  which  controls  the  lighting  as  well  as  the  ignition  circuit, 
is  shown  in  the  upper  left-hand  portion  of  the  figure.  The  ignition  cir- 
cuit is  controlled  by  means  of  the  right-hand  lever  on  this  switch.  The 
switch  is  mounted  on  the  instrument  board.  The  coil  is  shown  in  the 
upper  right-hand  corner  and  below  it  is  the  resistance  unit  followed  by 
the  interrupter  and  condenser  connected  in  parallel  between  the  resist- 


PIG.   158. — Elements  of  Cadillac  Eight  ignition  system. 

ance  unit  and  the  ground.  The  distributor,  with  its  leads  to  the  eight 
spark  plugs,  is  shown  to  the  left  of  the  condenser.  The  wiring  diagram 
of  the  system  is  shown  in  Fig.  159. 

The  interrupter,  the  distributor,  the  condenser,  and  the  automatic 
spark  advance  mechanism  are  all  located  in  a  compact  unit  mounted  on 
the  fanshaft  housing  and  are  driven  by  the  fanshaft  through  spiral  gears. 
Figure  160  is  a  view  of  the  Cadillac  engine  and  shows  the  ignition  unit 
mounted  between  the  blocks  on  the  fanshaft  housing.  One  feature  of 
this  installation  is  the  fact  that  the  ignition  unit  is  completely  enclosed  by 
a  metal  container,  and  has  metal  conduits  leading  from  the  unit  to  each 
cylinder  block  fco  carry  the  high-tension  spark  plug  wires.  The  cover 
protects  the  unit  from  dust,  and  the  conduits  protect  the  wires  from  acci- 
dental injury. 


MULTIPLE  CYLINDER  IGNITION  SYSTEMS 


125 


LINE 


SWITCH 


BATTERY 


DIST. 


SECONDARY 


,  RESISTANCE 

TIMER     £     UNIT 


•=•  —          —  DISTRIBUTOR  HEAD 

TO  SPARK   PLUGS 
FIG.  159. — Wiring  diagram,  Cadillac  Eight  ignition  system. 


//<?/#/  Conduit 
for  Spark 
Ptug  Cables- , 


ignition  Unit 


FIG.   160. — Cadillac  eight-cylinder  engine  showing  ignition  system. 


126 


AUTOMOTIVE  IGNITION  SYSTEMS 


Figure  161  is  a  sectional  view  of  the  ignition  unit  showing  the  dis- 
tributor at  the  top,  the  timer  or  interrupter  below,  and  the  automatic 
spark  advance  mechanism  in  the  bottom.  The  condenser  is  mounted  on 
the  right-hand  side  of  the  unit  in  a  waterproof  casing.  The  spark  timing 
is  controlled  automatically  by  the  automatic  spark  advance  mechanism 
which  advances  or  retards  the  position  of  the  timer  cam  relative  to  the 
driving  shaft,  as  the  engine  speed  increases  or  decreases.  A  spark  lever 
at  the  steering  wheel  is  provided,  however,  by  which  the  timing  may  be 


LOCKING  DEVICE  FOR  ALUMINUM  CAP 
ALUMINUM   CAP 


TO  SPARK  PLUGS 

TO  IGNITION  COIL 

CENTER  CONTACT 


LOCKING  CUP 

CONTACT  BUTTON 

OIL  CUP 

(MISPLACED   90°) 

PLATE  ON  ROTOR 
LOCK  SCREW  FOR  CAM 

DISTRIBUTOR  SHAFT 
BREATHER 

(MISPLACED    90°) 

CENTRIFUGAL  GOVERNOR 

WEIGHT 
MANUAL- 
CONTROL 
LEVER 


CONTACTS  CONNECTED 
TO  SPARK  PLUGS 
SCREW  HOLDING 
BRACKET  FOR  CONDUIT 
BRACKET  FOR  CONDUIT 
DISTRIBUTOR  HEAD 
ROTOR 

TIMER  CAM 

ESISTANCE  UNIT 


-CONDENSER 
GOVERNOR  SPRING 


AN SHAFT 
GEAR  ON  FANSHAFT 


GEAR   ON 

DISTRIBUTOR 

SHAFT 


FIG.  161. — Seotional  view  of  Cadillac  Eight  ignition  unit. 

further  advanced  or  retarded.     This  spark  lever  is  connected  to  the  man- 
ual control  lever  at  the  left  of  the  distributor  housing. 

The  timer  or  interrupter  used  on  this  system  is  shown  in  Fig.  162. 
The  striking  feature  of  this  timer  is  that  it  employs  two  sets  of  contact 
points.  The  eight-lobed  cam  on  the  timer  shaft  operates  two  contact 
arms.  These  contact  arms  and  the  contact  points  are  connected  into  the 
circuit  in  parallel,  as  shown  in  the  wiring  diagram  Fig.  159,  and  each  set 
of  contact  points  handles  but  one-half  of  the  primary  current,  thus  reduc- 


MULTIPLE  CYLINDER  IGNITION  SYSTEMS 


127 


ing  the  wear  and  also  the  pitting  and  burning  of  the  points.  To  ac- 
complish this,  however,  it  is  absolutely  necessary  that  both  sets  of 
contact  points  be  adjusted  to  open  at  exactly  the  same  instant  and  exactly 
the  same  amount.  The  proper  distance  between  points,  when  opened, 
is  .020  in.  This  adjustment  should  be  watched  carefully  and  kept  cor- 
rect because  if  one  set  of  contact  points  wears  slightly  more  than  the 
other  set,  the  one  set  will  open  first,  leaving  the  second  set  still  closed. 
The  primary  current  will  then  be  flowing  through  the  second  set.  When 
these  second  contacts  open,  the  arcing  and  pitting  will  be  as  bad  as  if 
the  first  set  of  contact  points  were  not  present.  This  latter  condition 
would,  of  course,  defeat  the  object  of  installing  the  two  sets  of  breaker 
points. 

87.  Firing  Order  of  Twelve-cylinder  Engines. — The  twelve-cylinder 
engine  has  two  blocks  of  six  cylinders  each.  The  blocks  are  arranged 
in  a  V  with  an  included  angle  of  60°  as  shown  in  Fig.  163.  One  block  of 


.    8 LOBE D  CAM, 

PRIMARY 
TERMINAL 


:s - 


•CONDENSER 


BREAKER  POINTS 

.(OPERATE  IN  PARALLEL) 


„  TIMING  ADJUSTING 
'     .     SCREW 

MANUAL  ZPARK 
ADVANCE  LEVER 


FIG.   162. — Delco  breaker  mechanism  used  on  Cadillac  Eight,  model  57. 

cylinders  is  usually  set  ahead  of  the  other  by  about  l>i  in.  to  permit  the 
lower  end  of  the  connecting  rods  of  opposing  cylinders  to  be  placed  side 
by  side  on  the  same  crank  pin.  The  crankshaft  is  of  the  conventional 
six-cylinder  type,  with  three  main  bearings,  similar  to  one  or  the  other  of 
the  forms  shown  in  Fig.  151. 

The  several  methods  of  numbering  the  cylinders  on  a  twelve-cylinder 
engine  are  shown  in  Fig.  164.  The  firing  order  in  each  block  is  similar 
to  that  in  a  six-cylinder  engine  and  is  usually  1,  5,  3,  6,  2,  4,  or  1,  4,  2,  6, 
3,  5,  with  the  cylinders  numbered  as  in  Fig.  164 A,  the  impulses  alternating 
from  one  side  to  the  other. 

On  the  Packard  engine,  numbered- as  in  Fig.  164A,  the  firing  order  is 
1R,  6L,  4R,  3L,  2R,  5L,  6R,  1L,  3R,  4L,  5R,  2L,  corresponding  to  a  firing 
order  for  each  block  of  1,  4,  2,  6,  3,  5.  On  the  Pathfinder,  numbered  as 
in  Fig.  1640,  the  firing  order  is  1R,  1L,  4R,  4L,  2R,  2L,  6R,  6L,  3R,  3L,  5R, 
5L.  This  order  is  the  same  as  used  on  the  Packard,  and  can  be  deter- 
mined by  a  careful  study  of  the  firing  orders  given  above  and  the  methods 
of  numbering  the  cylinders.  The  order  of  firing  for  the  National  twelve, 


128 


AUTOMOTIVE  IGNITION  SYSTEMS 


with  the  cylinders  numbered  as  in  Fig.  1645,  is  1,  12,  9,  4,  5,  8,  11,  2,  3, 
10,  7,  6.  This  corresponds  to  an  order  of  1,  5,  3,  6,  2,  4  for  each  block 
numbered  as  in  Fig.  164A. 


FIG.  163. — National  twelve-cylinder  engine. 


|  RADIATOR  |      |  RADIATOR  |     1  RADIATOR! 

LEFT    RIGHT        LEFT       RIGHT       LEFT    RK3HT 


ABC 

FIG.  164. — Numbering  of  cylinders  on  twelve-cylinder  engines v 

Perhaps  the  best  way  to  determine  the  firing  order  of  any  twelve- 
cylinder  engine  is  to  number  the  cylinders  of  the  right  block  starting  at 


MULTIPLE  CYLINDER  IGNITION  SYSTEMS 


129 


the  radiator  end  and  the  cylinders  of  the  left  block  starting  at  the  other 
end  of  the  engine  as  shown  in  Fig.  164C.  Considering  only  the  right 
block,  the  engine  should  be  cranked  by  haixd  with  the  priming  cocks  open 
or  the  spark  plugs  removed  until  cylinder  No.  1  on  the  right  block  is  on 
compression.  By  further  cranking,  it  can  be  determined  whether 
cylinder  No.  5  or  cylinder  No.  4  of  the  right  block  is  next  on  compression. 
If  No.  5  is  next,  the  firing  order  for  the  right  block  is  1,  5,  3,  6,  2,  4.  If 
No.  4  is  next,  the  firing  order  for  the  right  block  is  1,  4,  2,  6,  3,  5  as 
explained  in  Section  82  of  this  chapter.  Knowing  the  firing  order  of 
the  right  block,  the  firing  order  of  the  engine  is  found  by  following 
each  cylinder  on  the  right  block  by  the  cylinder  of  the  same  number  on 
the  left  block.  For  instance,  if  the  firing  order  of  the  right  block  is  1,  5, 


SPARK    PJLUGS  LEFT 

o  o©  ©  ©  < 


(SWITCH 


BATTERY 


DISTRIBUTOR 


SPARK   P|LUGS    RIGHT 

FIG.   165. — Wiring  diagram,  Packard  Twin  Six  ignition  system. 

3,  6,  2,  4,  the  firing  order  of  the  engine  is  1R,  1L,  5R,  5L,  3R,  3L,  6R,  6L, 
2R,  2L,  4R,  4L,  with  the  cylinders  numbered  as  in  Fig.  1 64C.  Knowing 
the  firing  order  with  the  cylinders  numbered  as  in  Fig.  164(7,  the  firing 
order  with  the  cylinders  numbered  as  in  Fig.  164A  or  in  Fig.  1Q4B  is  easily 
found. 

88.  The  Delco  Ignition  System  for  the  Packard  Twin  Six. — As  the  num- 
ber of  cylinders  is  increased  on  an  engine,  the  load  or  duty  imposed  on  the 
ignition  system  becomes  proportionately  greater.  The  ignition  systems 
for  the  four-  and  six-cylinder  engines  are  relatively  simple,  but  the  eight- 
and  twelve-cylinder  engines  require  special  means  for  producing  the 
large  number  of  sparks  required,  and  at  the  same  time  keep  the  wear  on 
contact  points  and  other  parts  down  to  a  reasonable  limit.  This  was 


130 


AUTOMOTIVE  IGNITION  SYSTEMS 


Interrupter 

Cam 


Interrupter 

Contact  Points 


Distributor 


Distributor  Gear- 


Manual  Spark 
Advance 


Distributor 
Brush 


Condenser 


Automatic  Jp&rk 
Advance  Mechanism 


FIG.  166. — Ignition  unit,  Packard  Twin  Six. 


MULTIPLE  CYLINDER  IGNITION  SYSTEMS 


131 


accomplished  on  the  Cadillac  Eight  by  providing  two  sets  of  breaker 
points  that  operate  in  parallel.  On  the  Packard  "Twin  Six,"  with  its 
high  speed  twelve-cylinder  engine,  the  same  result  is  accomplished  by  using 
a  coil,  an  interrupter,  and  a  distributor  for  each  block  of  six  cylinders. 
This  gives  practically  a  separate  ignition  system  for  each  block. 

The  primary  current  from  the  battery  divides  into  two  parallel  paths 
at  the  ignition  switch,  giving  each  block  an  individual  primary  circuit 
incorporating  a  coil,  a  breaker,  and  a  condenser.  This  arrangement 


Ignition 
Unit 
Prive 


r  v.f  *  ?  I..T  T  TTT 


I 


FIG.  167. — Front  view  of  Packard  Twin  Six  engine  showing  ignition  unit  drive. 

requires  two  distributors,  each  controlling  the  distribution  of  the  high- 
tension  secondary  current  to  the  six  cylinders  in  it's  respective  block. 
The  wiring  diagram  is  shown  in  Fig.  165. 

The  distributors,  the  breakers,  and  the  condensers  are  all  mounted 
in  the  vertical  ignition  unit  shown  in  Fig.  166.  The  upper  view  is  the 
breaker  box  containing  its  two  contact  arms,  one  for  each  primary  circuit. 
These  arms  are  operated  by  a  three-lobed  cam  that  revolves  at  crankshaft 
speed  thus  giving  three  sparks  in  each  block  per  revolution  of  the  crank- 
shaft, or  six  sparks  and  six  explosions  per  revolution  of  the  crankshaft  for 


132 


AUTOMOTIVE  IGNITION  SYSTEMS 


the  entire  engine.  The  two  breaker  arms  are  so  placed  that  the  points  in 
the  two  primary  circuits  open  in  the  proper  sequence  to  give  the  correct 
firing  order. 

Below  the  breaker  box  are  the  two  distributors,  one  on  either  side, 
driven  by  spiral  gears  from  and  at  one-half  the  speed  of  the  vertical  shaft 
which  carries  the  breaker  cam. 

Two  condensers,  one  for  each  pair  of  primary  contact  points,  are 
mounted  on  the  ignition  unit  housing.  These  condensers  serve  as  cover 
plates  for  openings  in  the  housing  through  which  the  automatic  spark 
advance  mechanism  in  the  lower  part  of  the  case  may  be  examined. 
The  ignition  unit  is  mounted  between  the  blocks  at  the  front  of  the  engine 
and  is  driven  by  spiral  gears  from  the  camshaft  as  shown  in  Fig.  167. 


FIG.  168. — Pierce- Arrow  ignition  unit  showing  condenser  mounting  and  driving  mechanism. 

89.  Delco  Ignition  for  Fierce-Arrow  Dual  Valve  Six. — The  Fierce- 
Arrow  Dual  Valve  Six  engine  is  distinctive  in  that  it  has  two  inlet  and 
two  exhaust  valves  and  two  spark  plugs  for  each  cylinder.  The  engine 
is  provided  with  a  dual  battery  ignition  system.  This  means  that  the 
ignition  system  is  equipped  with  two  independent  sets  of  spark  plugs, 
condensers,  breaker  points,  transforming  coils,  etc.  The  ignition  switch 
is  so  constructed  that  either  or  both  sets  of  ignition  may  be  operated 
at  will.  The  double  system  is  recommended  because  under  such  con- 
ditions two  spark  plugs  are  being  fired  synchronously  in  each  cylinder. 
This  means  a  considerable  increase  in  power  and  more  miles  per  gallon 
of  fuel  because  of  the  better  combustion  when  the  charge  of  gas  is 
ignited  from  two  points.  The  single  system  can  be  used  when  it  is 
desired  to  test  out  the  ignition  system,  or  under  special  conditions 
where  the  storage  battery  might  be  badly  discharged. 


MULTIPLE  CYLINDER  IGNITION  SYSTEMS 


133 


The  double  distributor,  Fig.  168,  is  equipped  with  an  automatic 
spark  advance  which  is  located  on  the  lower  part  of  the  vertical  shaft 
which  carries  the  interrupter  cam  H,  Fig.  169.  To  this  shaft  is  at- 
tached a  centrifugal  type  of  governor,  which  is  so  designed  that  as  the 
engine  speed  increases,  the  governor  weights  are  thrown  outward  by 
centrifugal  force.  The  movement  of  the  governor  weights  revolves 
the  top  of  the  interrupter  shaft  through  a  slight  angle  in  the  proper 
direction  to  advance  the  spark. 

The  battery  breaker  points  KL  and  EP,  Fig.  169,  should  be  set  to 
open  approximately  .015  in.  A  special  wrench  is  furnished  by  the  makers 


FIG.  169. — Pierce- Arrow  ignition  unit  showing    distributor  and  interrupter  mechanism. 

for  this  purpose  and  is  equipped  with  two  gages,  one  for  the  approxi- 
mate setting  of  the  spark  plug  gaps  and  the  other  for  the  approximate 
opening  of  the  breaker  points.  These  breaker  points  are  of  tungsten 
and  normally  need  but  little  attention;  in  instances  where  it  is  neces- 
sary to  adjust  the  points,  as  wearing  takes  place,  it  is  not  necessary 
to  take  special  pains  to  true  the  points  up  so  that  they  will  make  con- 
tact over  their  entire  surfaces,  as  they  have  a  tendency  to  true  them- 
selves up  in  service. 

Before  putting  a  car  into  service  it  is  advisable  to  put  a  little  vase- 
line around  the  track  in  the  distributor  heads  S  and  0,  Fig.  169,  on 
which  the  contact  button  Q  travels.  After  this  is  done,  any  excess 


134 


AUTOMOTIVE  IGNITION  SYSTEMS 


vaseline  should  be  wiped  from  the  track  with  a  dry  cloth.  In  other 
words,  it  is  not  desirable  to  permit  this  lubricant  to  remain  in  quanti- 
ties upon  the  surface  of  the  insulator. 

The  fiber  cams  F  and  /,  Fig.  169,  on  the  breaker  arms  will  wear 
slightly  in  the  first  few  hundred  miles  of  use.  After  the  car  has  been 
run  about  one  thousand  miles,  the  setting  of  the  breaker  points  should 
be  checked.  The  breaker  points  should  operate  in  exact  synchronism; 

that  is,  they  should  open  at  the 
same  instant,  or  the  advantage  of 
having  two  sets  of  spark  plugs  in 
each  cylinder  will  be  lost.  If  it  is 
desired  to  make  them  open  at  a 
point  more  closely  approaching  ex- 
act synchronism,  it  can  be  done  by 
loosening  the  three  screws  D,  Fig. 
169,  on  the  sub-base  to  which  these 
breaker  mechanisms  are  attached. 
After  the  screws  are  loosened,  the 
sub-base  may  be  moved  about  with- 
in limits  until  the  desired  equaliza- 
tion is  obtained.  The  screws 
should  then  be  tightened.  The 
firing  order  of  the  engine,  1,  5,  3,  6, 
2,  4,  is  imprinted  on  the  Bakelite 
distributor  heads  S  and  0,  Fig. 
169,  with  the  proper  cylinder 
number  opposite  each  terminal. 

For  timing  this  double  ignition 
system  with  the  engine,  the  fly- 
wheel should  first  be  placed  so  that 
the  indicator  is  over  the  " ignition" 
mark  on  the  flywheel  as  shown  in 
Fig.  170.  Care  should  be  taken  to 
see  that  the  engine  is  on  the  com- 
pression stroke  of  No.  1  cylinder 
when  this  is  done.  The  distribut- 
ing arms  in  the  Delco  unit,  Fig. 
168,  should  then  be  set  in  a  posi- 
tion to  be  firing  No.  1  cylinder  as  marked  on  the  head  of  the  dis- 
tributors. Both  sets  of  breaker  points  should  just  be  beginning  to  open 
with  the  spark  lever  fully  retarded.  In  this  position,  the  distributor  unit 
should  be  coupled  to  the  driving  flange. 

The  two  coils  used  with  this  double  system  are  mounted  on  the 
engine  side  of  the  dash  as  shown  in  Fig.  171.  Each  coil  carries  a^re- 


FIG.  170. — Position  of  flywheel  for  ignition 
timing  on  Fierce-Arrow  Dual  Valve  Six. 


MULTIPLE  CYLINDER  IGNITION  SYSTEMS 


135 


sistance  unit  to  protect  the  coils,  should  the  ignition  switch  be  ac- 
cidentally left  "ON"  with  the  engine  not  running.     The  wiring  diagram 


FIG.  171. — Dash  of  Pierce- Arrow  showing  location  of  ignition  coils. 

for  the  double  ignition  system  of  the  Fierce-Arrow  Dual  Valve  Six 
is  shown  in  Fig.  172. 


INTERRUPTERS- 
FIG.  172. — Wiring  diagram,  Fierce-Arrow  Dual  Valve  Six  ignition  system. 

90.   Ignition  Requirements  of  Liberty  Twelve  Aircraft  Engines. — 

The  service   expected   of  aircraft   engines  is  so  severe  and  exact  that 
nothing  is  overlooked  that  will  better  the  performance  of  these  engines. 


136 


AUTOMOTIVE  IGNITION  SYSTEMS 


The  life  of  the  aviator  and  the  success  of  his  flying  depend  on  the  con- 
sistent performance  of  all  parts  entering  into  the  construction  of  the 
power  plant.  The  ignition  systems  used  on  airplane  engines  have  been 
developed  to  keep  pace  with  the  improvements  made  in  other  parts. 
The  result  of  these  improvements  is  an  ignition  system  that  can  be 
depended  upon  to  deliver  a  spark  to  the  cylinder  under  practically 
any  condition  met  in  the  most  strenuous  military  service.  Two  com- 
plete and  independent  ignition  systems  are  provided,  either  of  which 
will  fire  all  twelve  of  the  engine  cylinders.  This  duplication  of  igni- 
tion system  precludes  the  possibility  of  the  engine  becoming  stalled, 

due  to  the  failure  of  the  ignition 
system.  The  two  systems  may  be 
used  at  the  same  time  giving  two 
sparks  in  each  cylinder,  an  advan- 
tage in  high  speed  flying. 

The  engine  is  cranked-  or  started 
by  pulling  over  on  compression  by 
means  of  the  propeller.  The  com- 
pression is  tested  by  rocking  the 
engine  back  and  forth  several  times 
by  the  propeller.  It  is  very  neces- 
sary that  the  engine  should  not  kick 
back  at  these  times  or  severe  injury 
to  the  mechanics  may  result.  The  in- 
terrupter used  on  the  aircraft  engines 
was  developed  with  this  in  mind 
making  a  back  kick  impossible.  The 
method  of  accomplishing  these  re- 
sults, as  explained  by  the  Equipment 
Division  of  the  U.  S.  A.  Signal  Corps, 
is  given  in  the  following  paragraphs. 
91.  The  Delco  Ignition  System 
for  Liberty  Twelve  Aircraft  Engines. 

The  ignition  system  used  on  the  " Liberty  Twelve"  aero  engines  is  known 
as  the  generator-battery  type.  This  system  comprises  two  independent 
breaker  and  distributor  mechanisms  or  heads,  identical  in  every  respect 
and  each  firing  all  twelve  cylinders.  These  distributors  are  supplied 
with  electrical  energy  from  two  sources.  For  starting  and  for  idling 
speeds  up  to  650  r.p.m.  current  is  drawn  from  a  specially  constructed 
four-cell  storage  battery.  This  battery,  Fig.  173,  is  very  light  and  carries 
very  little  liquid  or  electrolyte  (barely  enough  to  fill  a  hydrometer  syringe, 
besides  what  is  absorbed  by  the  plates  and  separators).  Nevertheless,  it 
has  sufficient  capacity  to  ignite  the  engine  at  full  speed  for  three  hours. 
It  is  so  constructed  that,  even  though  it  be  turned  upside  down,  it  will 
still  continue  to  function  properly. 


FIG.    173. — Special    storage    battery   for 
airplane  service. 


MULTIPLE  CYLINDER  IGNITION  SYSTEMS  137 

Generator. — In  addition  to  the  battery,  a  positively  driven  generator 
is  provided,  so  geared  that  it  runs  at  one  and  one-half  times  crankshaft 
speed.  As  stated  above,  electrical  energy  for  starting  and  idling  speeds 
is  supplied  by  the  battery.  As  the  engine  speed  is  increased,  the 
generator  " builds  up"  and  its  output  grows  greater  until,  at  about  650 
r.p.m.,  the  generator  voltage  equals  that  of  the  battery.  The  maximum 
generator  output  exceeds  the  requirements  for  ignition  so  that,  at  a 
speed  above  650  r.p.m.,  the  direction  of  flow  of  current  is  reversed  and 
the  excess  output  of  the  generator  goes  to  recharge  the  battery.  The 
rate  at  which  the  battery  will  be  recharged  will  depend  upon  the  condi- 
tion of  the  battery.  With  an  almost  discharged  battery,  the  rate  will 
be  about  10  amperes,  but  will  diminish  as  the  battery  voltage  rises  until 
the  battery  is  completely  charged,  when  the  charging  rate  vill  be  just 
sufficient  to  maintain  the  battery  in  a  properly  charged  condition. 

Regulation. — The  generator  is  controlled  by  a  voltage  regulator  which 
prevents  the  output  exceeding  a  predetermined  figure.  In  view  of  this 
fact,  the  generator  will  supply  current  for  ignition  indefinitely,  without 
the  battery,  as  long  as  the  engine  speed  is  not  allowed  to  drop  below  500 
r.p.m.  It  is  not  possible  to  crank  the  engine  fast  enough  to  start  it  on 
the  generator,  however. 

Switch. — A  duplex  ignition  switch  is  provided  which  will  permit  either 
one  or  both  distributors  to  be  turned  "ON. "  This  switch  is  so  con- 
structed that  either  ignition  set  can  be  used  alone  without  connecting 
in  the  generator.  In  starting,  only  one  side  should  be  used  since  with 
both  switches  "ON"  the  generator  is  connected  to  the  battery.  Under 
this  condition,  the  discharge  from  the  battery  through  the  generator 
before  the  engine  is  started  would  be  an  excessive  drain  on  the  battery. 
It  is  essential,  however,  that  both  switches  be  "ON"  at  all  flying  speeds. 
The  ignition  switch  has  an  ammeter  incorporated  in  it,  and  this  ammeter 
indicates  the  amount  of  current  flowing  to  or  from  the  storage  battery. 
If  the  ammeter  shows  a  discharge  at  any  speed  above  650  or  700  r.p.m., 
with  both  switches  "ON,"  it  is  an  indication  that  something  is  wrong 
with  the  generator  circuit  and  that  all  electrical  energy  is  being  supplied 
from  the  battery.  If  the  ammeter  stands  at  zero,  under  the  same  condi- 
tions, it  indicates  that  the  storage  battery  is  not  receiving  a  charge,  but 
that  the  ignition  is  being  carried  by  the  generator. 

Distributors. — The  interrupter,  the  condenser,  the  distributor,  and 
the  coil  are  all  contained  in  one  compact  unit.  Two  of  these  units  are 
provided,  one  being  mounted  near  the  top  of  each  row  of  cylinders 
as  is  shown  in  Fig.  174.  These  units  are  driven  direct  from  the 
camshafts,  which  are  mounted  above  the  two  rows  of  cylinders.  The 
interior  construction  of  the  interrupter  is  shown  in  Fig.  175.  The  circuit 
breaker  mechanism  for  each  of  the  distributor  heads  is  identical  with 


138 


AUTOMOTIVE  IGNITION  SYSTEMS 


FIG.  174. — Liberty  Twelve  aircraft  engine  showing  location  of  ignition  units. 


MULTIPLE  CYLINDER  IGNITION  SYSTEMS 


139 


that  used  in  high-grade  magneto  or  battery  ignition  systems,  with  two 
exceptions,  as  follows:  Two  main  circuit  breakers,  connected  in  parallel, 
are  provided  instead  of  one.  The  two  breakers  are  timed  to  operate 
simultaneously  and  are  provided  in  duplicate  as  a  precautionary  measure. 
An  auxiliary  circuit  breaker,  the  function  of  which  is  to  prevent  the  pro- 
duction of  a  spark  when  the  engine  is  turned  backward  or  "rocked,"  is 
also  provided.  This  auxiliary  breaker  is  connected  in  parallel  with  the 
other  two  through  a  resistance  unit  which  reduces  the  amount  of  current 
flowing  through  it.  The  breaker  is  so  timed  that  it  opens  slightly  before 


FIG.  175. — Interrupters,  Liberty  Twelve  aircraft  engine  ignition  system. 

the  other  two  when  the  engine  is  turned  in  a  forward  direction.  The 
opening  of  the  main  breakers  then  results  in  the  production  of  a  spark. 
When  the  engine  is  turned  in  a  backward  direction,  the  two  main  breakers 
open  first  and  no  spark  is  produced,  due  to  the  fact  that  the  current  con- 
tinues to  flow  through  the  coil  through  the  auxiliary  breaker,  but  in 
diminished  quantity,  due  to  the  resistance  unit.  By  the  time  the  circuit 
is  opened,  at  the  auxiliary  breaker,  the  intensity  of  the  magnetic  field  of 
the  coil  has  weakened  to  such  an  extent  that  no  spark  is  produced.  This 
action  prevents  an  explosion  in  the  cylinder,  when  the  engine  is  being 


140 


AUTOMOTIVE  IGNITION  SYSTEMS 


cranked  backwards,  or  when  it  rocks  back  after  being  pulled  over  on 
compression.  An  unexpected  explosion  in  the  engine  might  result  in 
severe  injury  to  the  men  handling  the  propeller  when  starting  the 
.engine. 

The  advantages  this  system  presents  over  the  magneto  system  are: 
1.  Easy  starting — a  spark  of  greater  intensity  is  produced  at  cranking 
speed  than  at  flying  speed.  , 


FeHWath«» 


Driving  Flange       j 


Distributer  Sha»t_ 


Bearing  Retainer. 


Call 


Rotor  Arm 


Refer  Brush 


Low  Tension 
Uarf  to  Switch 


FIG.  176. — Cross  section  of  Liberty  Twelve  aircraft  engine  distributor,  showing  location 

of  coil. 

2.  Reliability — two  distinct  distributor  mechanisms,  each  igniting  all 
twelve  cylinders  through  separate  spark  plugs,  each  distributor  head 
being  fitted  with  two  sets  of  breaker  arms  and  contact  points.     Two 
distinct  sources  of  electrical  energy — the  battery  and  the  generator. 

3.  Safety — the  auxiliary  breakers  prevent  the  possibility  of  a  back  kick. 
The  transformer  or  induction  coil  is  incorporated  in  the  Bakelite 

insulation  cover  of  each  distributor  head  as  shown  in  Fig.  176.     This 


MULTIPLE  CYLINDER  IGNITION  SYSTEMS 


141 


location  of  the  coil  is  ideal  as  it  is  completely  covered  and  protected  from 
damage  and  is  also  close  to  the  distributor  and  interrupter  so  that  very 
little  wiring  is  needed  to  connect  the  coil  into  the  circuits.  The  wiring 
incorporated  in  and  is  well  protected  by  the  hard  insulation.  The  wiring 
diagram  of  the  complete  electrical  equipment  is  shown  in  Fig.  177.  No 
automatic  spark  advance  mechanism  is  used,  the  time  of  the  spark  being 
controlled  by  the  aviator  by  means  of  a  small  hand  lever  conveniently 
located  on  the  control.  A  second  lever  controls  the  throttle.  It  has 
been  found  that  the  automatic  spark  advance  is  not  adaptable  to  aircraft 
engines,  the  highly  trained  aviator  being  able  to  carry  the  spark  at  the 
proper  point  for  best  engine  performance  at  all  speeds.  The  lack  of  an 
automatic  spark  advance  mechanism  eliminates  many  of  the  complicated 
parts  of  the  automobile  ignition  system  and  tends  to  promote  reliability 
and  to  better  the  performance  of  the  craft  upon  which  this  system  is  used. 


FIG.  177. — Circuit  diagram  of  Liberty  Twelve  aircraft  engine  ignition  system. 

92.  Ignition  Timing  on  Eight-  or  Twelve -cylinder  Engines. — The 
timing  of  the  ignition  system  on  an  eight-  or  twelve-cylinder  engine  is 
very  little  different  from  the  timing  of  a  four-  or  six-cylinder  ignition 
system.  The  same  method  is  employed  in  each  case.  The  firing  order 
of  the  engine  should  be  determined  by  the  method  described  in  this 
chapter.  The  next  step  is  to  set  cylinder  No.  1  on  the  firing  position, 
which  is  generally  5°  (on  the  flywheel)  past  upper  dead  center  on  the 
working  or  expansion  stroke.  Then  with  the  spark  level  fully  retarded, 
the  screw  holding  the  breaker  cam  should  be  loosened  and  the  breaker 
cam  turned  until  the  breaker  points  are  just  opening  and  the  distributor 
arm  is  on  the  distributor  segment  having  the  high-tension  cable  leading 
to  the  spark  plug  in  cylinder  No.  1.  The  breaker  cam  should  be  tightened 
in  this  position,  and  the  remaining  high-tension  cables  connected  to 
the  plugs  in  the  cylinders  according  to  the  firing  order  previously 
determined,  going  around  the  distributor  in  the  direction  of  rotation  of 
the  distributor  arm. 


CHAPTER  VI 
THE  LOW-TENSION  MAGNETO 

93.  Magneto  Classification. — The  magneto,  which  is  used  very 
extensively  for  ignition  purposes  on  automobiles,  trucks,  and  tractors, 
consists  essentially  of  two  parts,  the  magnets  which  supply  the  magnetic 
field,  and  the  armature  which  carries  the  winding  and  which  usualty 
must  revolve  in  this  magnetic  field  in  order  to  generate  a  current.  The 
magneto  is  built  in  two  general  types  according  to  the  methods  employed 
for  generating  the  current,  namely,  the  armature  wound  or  H  type  and 
the  inductor  type.  In  the  armature  wound  type,  the  current  is  generated 


FIG.   178. — Bar  and  horseshoe  magnets. 

in  a  winding  revolving  in  and  cutting  the  magnetic  field.  In  the  inductor 
type,  the  winding  in  which  the  current  is  generated  is  stationary.  The 
current  is  generated  by  the  reversal  of  the  magnetism  through  the  coil 
and  the  cutting  of  the  winding  by  lines  of  force.  The  magneto  may  also 
be  classified  either  as  high-  or  low-tension,  according  to  the  voltage  of  the 
current  which  it  generates.  Both  the  high-  and  low-tension  magnetos 
may  be  constructed  on  either  the  armature  wound  or  the  inductor 
principle. 

94.  Magneto  Magnets. — It  is  a  well-known  fact  that  either  in  a  bar 
magneto  or  in  a  magnet  bent  in  the  shape  of  a  horseshoe,  as  in  Fig.  178, 
the  magnetic  strength  is  concentrated  near  the  ends,  as  indicated  by  the 
bunches  of  iron  filings  at  the  ends  of  these  magnets.  One  end  of  the  mag- 

143 


144 


AUTOMOTIVE  IGNITION  SYSTEMS 


net  is  called  the  North  or  N-pole,  and  the  other  the  South  or  S-pole.  The 
difference  between  the  two  poles  can  be  seen  by  taking  two  horseshoe 
magnets  and  placing  their  like  poles  and  again  their  unlike  poles  together. 
It  will  be  found  that  the  like  poles  repel  each  other  and  the  unlike  poles 
attract  each  other.  This  is  one  of  the  fundamental  laws  of  magnetism. 
95.  Lines  of  Force. — If  a  horseshoe  magnet  be  placed  on  its  side,  as 
shown  in  Fig.  179 A,  a  piece  of  paper  put  over  it,  and  iron  filings  sprinkled 
over  the  paper  it  will  be  found  that  the  filings  arrange  themselves  in  well 
defined  lines.  This  arrangement  indicates  that  there  is  a  magnetic  force 
acting  between  the  two  poles  of  the  magnet.  The  influence  which  two 
horseshoe  magnets  (such  as  used  on  magnetos)  have  on  each  other,  when 
laid  side  by  side,  is  clearly  shown  in  Fig.  179  B  and  C.  In  Fig.  1795 
two  magnets  are  arranged  in  a  vertical  position  to  show  the  magnetic 
flux  between  the  pole  ends  when  properly  assembled;  while  in,  Fig.  179C, 
the  magnets  are  incorrectly  assembled,  the  North  end  of  one  magnet 


FIG.  179. — Magnetic  field  shown  by  iron  filings. 

lying  next  to  the  South  end  of  the  other,  thereby  greatly  reducing  the 
number  of  lines  of  force  that  would  be  cut  by  an  armature  rotating  be- 
tween the  poles.  In  placing  the  magnets  on  a  magneto,  great  care  must 
be  taken  to  get  all  the  North  poles  together  and  all  the  South  poles  to- 
gether. An  easy  way  to  make  sure  of  this,  before  putting  the  magnets 
on  the  magneto,  is  to  lay  the  magnets  together  so  that  the  poles  will 
repel  each  other. 

96.  Types  of  Magnets. — In  some  types  of  magnetos,  compound 
permanent  magnets  are  used.  A  compound  magnet  is  one  built  up  of 
several  simple  magnets  arranged  with  like  poles  together  as  shown  in  Fig. 
180(7.  Experience  has  proved  that  a  compound  magnet  is  much  stronger 
than  a  simple  magnet  of  the  same  size,  and  is,  therefore,  more  desirable. 
The  number  of  magnets  required  to  produce  the  desired  magnetic  field 
strength  depends  to  a  great  extent  on  both  the  kind  and  the  quality  of 
the  steel  used  in  the  magnets.  At  the  present  time,  chrome  or  tungsten 


THE  LOW-TENSION  MAGNETO 


145 


steel  is  most  generally  used,  so  that  two  magnets,  arranged  as  shown  in 
Fig.  180B,  are  usually  found  sufficient.  It  is  generally  recognized  that 
the  magnetic  pull  of  each  magnet  should  be  able  to  sustain  a  weight  of  at 
least  15  Ib.  in  order  to  give  satisfactory  service. 


Simple  magnet 
A. 


Double  magnet 

B. 
FIG.  180. 


Compound  magnet 
C. 


97.  Mechanical  Generation  of  Current. — It  has  been  found  that  if  a 
wire  be  moved  across  the  magnetic  field  between  the  poles  of  a  magnet 
so  as  to  cut  the  lines  of  force,  there  will  be  an  electric  current  generated 
in  the  wire.  If  the  wire  should  then 
be  moved  across  the  lines  of  force  in 
the  opposite  direction,  the  current 
would  again  flow  in  the  wire  but  in 
the  opposite  direction.  The  exact 
reason  for  this  is  unknown,  but  it  is 
a  well-known  fact  that  cutting  mag- 
netic lines  of  force  by  moving  a  wire 
across  them  will  generate  current  in 
the  wire.  The  process  of  generating 
a  current  in  this  manner  is  known  as 
induction,  and  the  current  thus  pro- 
duced is  termed  an  induced  current. 

The  fact  that  current  can  be  gener- 
ated through  induction  is  made  use 
of  in  the  magneto,  an  elementary  type 
of  which  is  shown  in  Fig.  181.  The 
wire  is  formed  in  the  shape  of  a  rec- 
tangle and  arranged  to  rotate  between 
the  pole  pieces  of  the  magnet.  If  the  ends  of  the  wire  are  con- 
nected by  a  measuring  instrument,  a  current  of  electricity  will  be  found 
to  flow  out  of  one  end  of  the  wire  and  into  the  other  end  as  the  wire  is 
revolved.  In  the  position  shown,  with  the  loop  rotating  in  a  clockwise 
10 


FIG. 


ROTATING  ARMATURE 
181. — Mechanical     generation     of 
current. 


146 


AUTOMOTIVE  IGNITION  SYSTEMS 


direction,  the  current  will  flow  out  at  B  and  in  at  A.  If  the  loop  of  wire 
is  turned  through  a  complete  revolution,  it  will  be  found  that  the  current 
generated  will  alternate  in  direction,  making  one  complete  reversal  in  one 
revolution  of  the  wire.  This  is  due  to  the  wire  cutting  the  magnetic 
lines  of  force  first  in  one  direction,  and  then  in  the  other.  When  the  wire 
is  cutting  the  lines  of  force  at  right  angles,  the  voltage  is  the  maximum, 
and  it  is  at  this  period  of  rotation  that  the  current  is  best  for  ignition 
purposes.  This  condition  occurs  twice  during  a  complete  revolution 
of  the  loop  of  wire.  A-B  represents  the  position  of  maximum  in- 
duced voltage,  and  A'-B'  the  point  of  no  induced  voltage  since  at  this 
point  the  wire  is  travelling  parallel  to  the  lines  of  force  and  is,  therefore, 
not  cutting  them.  After  passing  the  vertical  position,  the  side  of  the 
loop  A  will  cut  the  magnetic  lines  of  force  in  the  opposite  direction, 
causing  the  induced  current  in  the  wire  to  reverse,  flowing  out  at  A 
instead  of  at  B. 


FIG.  182. — Change  of  magnetic  field  through  H-type  armature. 


In  the  actual  magneto,  instead  of  having  only  one  turn  of  wire,  a  great 
many  turns  of  wire  are  wound  in  the  shape  of  a  coil  around  a  piece  of 
laminated  iron,  called  the  arrhature  core.  This  coil  is  caused  to  rotate 
between  the  magnetic  poles,  thus  generating  a  current.  Figure  182 
illustrates  the  change  and  cutting  of  the  magnetic  lines  of  force  during 
one  complete  revolution  of  the  armature.  By  using  the  laminated  iron 
armature  core,  the  strength  of  the  magnetism  between  the  poles  of  the 
magnet  is  increased,  thus  increasing  the  number  of  lines  of  force  that  are 
cut  by  the  coils  of  wire. 

98.  Low -and  High-tension  Magnetos. — A  low-tension  magneto  is  one 
which  delivers  current  of  a  low  voltage.  This  current  must  be  converted 
to  the  necessary  high  voltage  for  ignition  by  an  external  induction  or  trans- 
former coil.  The  armature  contains  only  a  primary  winding,  while  the 
transformer  coil  has  the  usual  primary  and  secondary  windings. 

A  high-tension  magneto  delivers  current  from  the  armature  at  suffi- 
ciently high  voltage  for  ignition,  without  the  use  of  an  external  trans- 
former coil.  The  high-tension  current  is  generated  in  a  high-tension 


THE  LOW-TENSION  MAGNETO 


147 


winding  on  the  armature  of  the  magneto.  The  armature  assembly  also 
contains  the  primary  winding  and  the  condenser.  The  true  high-tension 
magneto  must  not  be  confused  with  the  so-called  high-tension  magneto 
in  which  the  armature  current  is  transformed  by  a  coil  placed  in  the  top 
of  the  magneto,  instead  of  outside  as  is  done  in  the  low-tension  type. 
The  coil  is  contained  in  the  magneto  assembly  merely  for  convenience, 
but  this  does  not  make  it  a  high-tension  magneto  in  the  correct  sense  of 
the  term. 

99.  Armature  and  Inductor  Type  Magnetos. — An  armature  or  shuttle 
wound  type  magneto  is  one  in  which  the  lines  of  force  are  cut  by  means 
of  a  coil  of  wire  wound  on  an  armature  or  shuttle  rotating  between  the 
magnetic  pole  pieces  as  just  described.  It  may  be  of  either  the  high-  or 
low-tension  type. 

In  an  inductor  type  magneto,  the  coil  of  wire  is  stationary.  The 
cutting  of  the  lines  of  force  by  the  stationary  coil  is  caused  by  a  revolving 
inductor.  Since  the  coil  in  which  the  current  is  generated  is  stationary, 


210"      240"     270°      300°      330 


30" 


FIG.   183. — Typical  curve  of  current  from  shuttle  armature. 

this  avoids  the  necessity  of  having  sliding  contacts  and  brushes  in  order 
to  connect  the  coil  with  the  external  circuit.  The  inductor  type  magneto 
may  also  be  either  low-  or  high-tension.  The  constructional  features  of 
these  two  general  types  will  be  pointed  out  in  considering  the  several 
types  of  modern  magnetos. 

100.  Current  Wave  from  a  Shuttle  Wound  Armature.— Figure  183 
shows  a  typical  curve  of  the  current  generated  in  the  winding  of  a  shuttle 
wound  armature  as  it  turns  through  one  revolution.  In  Fig.  184  are 
shown  the  positions  of  the  armature  corresponding  to  the  points,  A,  B, 
C,  D,  and  E  of  Fig.  183.  In  position  A  the  flux  is  passing  through  the 
armature  in  one  direction  while  in  position  E,  after  turning  180°,  the 
flux  is  in  the  other  direction,  because  the  armature  has  turned  around. 
During  the  remainder  of  the  revolution,  from  position  E  around  to  posi- 
tion A,  the  current  generated  will  be  opposite  in  direction  to  that  gen- 
erated during  the  first  half  of  the  revolution.  The  current  generated 
during  the  first  half  of  the  revolution  is  shown  in  Fig.  183  by  the  height 
of  the  curve  above  the  base  line,  while  that  generated  during  the  second 
half  is  shown  below  the  line. 


148 


AUTOMOTIVE  IGNITION  SYSTEMS 


The  exact  positions  of  the  armature  at  which  the  strongest  electrical 
impulses  can  be  obtained,  and  also  the  shape  of  the  current  wave,  depend 
upon  the  forms  of  the  pole  pieces  and  the  armature  core,  as  well  as  upon 
the  speed  of  rotation  and  the  strength  of  the  magnets.  Any  change  in 
one  of  these  factors  will  produce  a  change  in  the  electrical  pressure  at  the 
terminals' of  the  armature  winding. 

.Most  magnetos  that  are  run  at  variable  speeds  are  constructed  so 
that  a  strong  current  can  be  produced  throughout  a  considerable  range 
of  position  of  the  armature.  This  is  done  to  allow  for  the  advance  and 
retard  of  ignition  relative  to  the  position  of  the  pistons,  as  well  as  to 
allow  for  the  lag  of  the  current  in  the  armature  with  regard  to  the  position 
of  the  armature  at  the  instant  of  maximum  impulse  or  voltage.  This 
current  lag  for  the  speeds  in  usual  practice  is  small,  so  that  in  general  the 
positions  of  the  armature  for  the  maximum  current  are  as  indicated  in 
Fig.  183  and  Fig.  184. 

101.  Magneto  Speeds. — It  is  evident  from  the  current  wave  diagram 
of  Fig.  183  that,  whatever  the  system  of  ignition  with  which  a  low-tension 
magneto  is  used,  the  best  spark  will  be  produced  only  during  the  angle  of 


A=o- 


1 


B  =  65"  C  =  95°  D  =  135' 

FIG.   184. — Armature  positions  of  Fig.  183. 


E=-180' 


rotation  in  which  the  current  generated  is  at  or  near  its  maximum.  When 
the  armature  is  in  position  C,  Fig.  184,  the  current  is  at  its  maximum  and 
the  spark  is  strongest.  As  the  armature  rotates  from  position  C  to 
D  the  curve,  Fig.  183,  is  near  its  maximum  height;  hence,  during  this 
period  the  current  produced  is  most  favorable  for  ignition  purposes. 
Position  C  would  correspond  to  extreme  advance  and  D  to  extreme  retard 
for  this  magneto,  giving  a  spark  range  of  about  40°  of  armature  rotation. 
It  is  evident  from  the  shape  of  the  curve  that  a  position  of  advance  beyond 
C  or  of  retard  beyond  D  would  give  a  spark  too  weak  for  ignition  purposes 
or  no  spark  at  all.  This  shows  the  necessity  of  having  an  alternating 
current  magneto  gear-driven  from  the  engine  shaft,  so  that  the  armature 
will  always  be  in  the  proper  position  with  relation  to  the  engine  pistons. 
The  curve  of  Fig.  183  also  shows  that  there  are  two  points  in  a  revolution 
of  this  type  of  armature  during  which  a  spark  can  be  obtained,  namely, 
between  C  and  D  as  just  mentioned  and  at  a  similar  position  180°  later, 
when  the  current  is  in  the  other  direction.  Consequently,  the  magneto 
with  an  H  type  or  shuttle  wound  armature,  ordinarily  used  for  automobile 
ignition,  gives  two  sparks  per  revolution  of  its  armature.  Because  of  this, 


THE  LOW-TENSION  MAGNETO 


149 


the  armature  speed  of  a  magneto  must  have  a  definite  relation  to  the 
number  of  cylinders  of  the  engine.  In  a  four-cylinder  four-stroke  engine 
the  armature  must  revolve  at  crankshaft  speed  in  order  to  produce  four 
sparks  during  two  revolutions  of  the  engine  crankshaft.  On  a  six-cylinder 
four-stroke  engine  the  armature  must  make  three  revolutions  during  two 
revolutions  of  the  crankshaft,  or  it  must  turn  at  one  and  one-half  times 
crankshaft  speed. 

102.  Low-tension  Magneto  Ignition  System  with  Interrupted  Primary 
Current. — In  this  type  of  ignition  system,  the  current  is  supplied  at  low 
voltage  by  a  low- tension  magneto  and  is  stepped  up  to  a  high  voltage  by 
an  induction  coil  similar  to  the  non-vibrating  coil  used  with  a  battery 

Spark  P/uos 
r_c — , ^f 


Distributor 
(on  Magneto] 


FIG.  185. — Low-tension  magneto  ignition  system  with  interrupted  primary  current. 

ignition  system.  The  mechanical  interrupter  for  the  primary  or  low- 
tension  current,  and  the  distributor  for  the  high-tension  current,  are 
provided  on  the  magneto.  Figure  185  shows  this  system  in  its  simplest 
form.  A  magneto  with  a  shuttle  wound  armature  is  shown,  although  a 
magnet  of  the  inductor  type  could  be  used  as  well.  One  end  of  the  arma- 
ture winding  is  grounded  to  the  metal  of  the  armature  as  is  usual  in 
magnetic  construction.  The  current  is  collected  from  the  other  end  of 
the  winding  by  a  collector  ring  and  brush  which  are  not  shown.  The 
interrupter  is  shown  separate,  but  it  is  always  mounted  on  the  magneto 
shaft  so  that  the  time  of  opening  the  circuit  is  in  proper  time  with  the 
period  of  greatest  current  flow  in  the  armature  winding.  Assuming  the 
interrupter  contacts  to  be  closed,  the  low-tension  current  generated  in 


150  AUTOMOTIVE  IGNITION  SYSTEMS 

the  armature  winding  flows  through  the  switch  and  the  primary  winding 
of  the  coil  and  through  the  interrupter  to  the  ground  (on  the  armature 
shaft)  and  back  into  the  armature  winding.  During  the  next  half 
revolution  of  the  armature,  the  current  in  the  circuit  is  in  the  reverse 
direction.  At  the  desired  time  for  the  spark,  which  must  be  during  the 
period  of  maximum  current  flow,  the  primary  circuit  is  broken  at  the 
interrupter.  This  is  caused  by  the  high  point  of  the  cam  raising  the 
interrupter  lever  from  its  contact  with  the  fixed  contact  point.  A 
condenser  placed  in  parallel  with  the  interrupter  absorbs  the  induced 
current  in  the  primary  winding,  caused  by  this  sudden  interruption  of 
the  current  flow,  and  assists  in  rapidly  breaking  down  the  magnetism  of 
the  coil  core,  in  the  same  manner  as  in  a  battery  ignition  system.  By 
this  action,  a  high-tension  current  is  induced  in  the  fine  secondary 
winding  of  the  coil.  The  distributor,  which  is  mounted  on  the  magneto, 
receives  this  current  at  its  central  connection  and  directs  it  to  the  proper 
plug. 

The  secondary  winding  of  the  coil,  as  shown,  is  entirely  separate 
from  the  primary  and  has  its  own  ground  connection.  This  is  not 
necessary  as  the  two  coils  could  be  connected  at  their  upper  ends  and 
the  secondary  ground  be  made  through  the  armature  to  the  grounded 
end  of  that  winding.  The  connection  to  the  distributor  would  then 
be  made  from  the  other  end  of  the  secondary  winding. 

Instead  of  having  the  switch  in  series  with  the  armature,  and  the 
circuit  through  the  coil  and  the  interrupter,  so  that  opening  the  switch 
breaks  the  circuit,  the  switch  connection  might  be  from  the  insulated 
side  of  the  circuit  to  the  ground.  In  this  case,  the  circuit  would  be 
through  the  coil  and  the  interrupter  when  the  switch  was  open.  When 
the  switch  was  closed,  the  current  would  have  a  permanent  and  easy 
path  to  the  ground  and  back  into  the  armature,  so  that  practically 
no  current  would  flow  through  the  coil  and  the  interrupter.  In  this 
case,  closing  the  switch  would  ground  the  primary  current  so  that  the 
coil  would  become  inoperative  and  ignition  would  cease. 

.  The  interrupter  cam  has  two  lobes  corresponding  to  the  two  cur- 
rent waves  produced  per  revolution  in  the  shuttle  type  of  armature 
and  also  in  some  magnetos  of  the  indicator  type.  This  arrangement 
is  used  when  the  number  of  cylinders  is  such  that  each  current  wave 
can  be  used  for  the  production  of  a  spark,  and  is  common  for  four-  and 
six-cylinder  engines. 

103.  Low -tension  Magneto  Ignition  System  with  Interrupted  Shunt 
Current. — The  interrupter  in  this  system  is  not  in  series  with  the  cir- 
cuit through  the  primary  winding  of  the  coil,  but  is  in  a  shunt  or  cross 
connection  as  shown  in  Fig.  186.  This  system  is  the  one  commonly 
used  when  a  low-tension  magneto  is  employed  for  ignition.  The  pri- 
mary current  has  two  possible  paths,  either  through  the  interrupter, 


THE  LOW-TENSION  MAGNETO 


151 


if  that  is  closed,  or  through  the  primary  winding  of  the  coil.  The 
current  naturally  takes  the  easy  path  through  the  interrupter,  when 
that  is  closed,  there  being  practically  no  current  through  the  coil  at 
this  time.  When  the  magneto  armature  reaches  the  desired  position 
for  the  spark,  which  is  at  some  point  during  the  period  of  maximum 
current  flow,  the  interrupter  is  opened.  This  sudden  interruption  of 
the  current  through  the  shunt  circuit,  combined  with  the  action  of  the 
condenser,  produces  an  induced  current  in  the  armature  circuit,  and 
this,  having  no  other  path,  rushes  instantly  through  the  primary 
winding  of  the  coil.  This  sudden  current  through  the  primary  winding 
induces  a  powerful  momentary  voltage  in  the  secondary  winding,  and 
this  voltage  is  used  for  the  production  of  the  spark  at  the  plugs. 


Spark  Plugs 
r~"T""T~ 


FIG.   186. — Low- tension  magneto  ignition  system  with  interrupted  shunt. 

It  will  be  noted  that  the  spark  from  this  type  of  magneto  is  pro- 
duced by  the  building  up  of  the  magnetic  field  of  the  coil  instead  of 
by  the  breaking  down  of  the  field  as  in  the  interrupted  primary  system 
previously  described.  For  this  reason,  and  also  because  of  the  resem- 
blance of  its  action  to  that  of  the  ordinary  transformer,  the  coil  is  some- 
times called  a  transformer  coil.  An  induced  voltage  is  created  in  the 
secondary  of  any  coil  when  the  magnetic  field  is  built  up  as  well  as  when 
it  is  broken  down.  In  battery  ignition  systems,  however,  the  action 
of  building  up  is  comparatively  slow,  and  the  induced  current  is,  there- 
fore, not  of  sufficient  voltage  to  be  used.  In  the  interrupted  shunt 
type  magneto,  the  coil  winding  of  the  armature,  coupled  with  a  con- 
denser of  proper  capacity,  produces,  on  the  break  of  the  shunt  circuit 
by  the  interrupter,  an  impulse  of  current  of  sufficient  power  to  mag- 
netize the  coil  very  rapidly  and  to  give  the  desired  induced  voltage  in 
the  secondary  winding. 


152 


AUTOMOTIVE  IGNITION  SYSTEMS 


After  the  armature  has  passed  the  position  of  maximum  current, 
the  interrupter  is  closed  and  the  armature  again  has  the  easy  shunt 
path  through  which  to  build  up  its  current,  when  it  again  rotates  into 
the  position  of  maximum  current. 

As  shown  in  the  diagram  of  Fig.  186,  the  coil  has  a  common  ground 
connection  for  the  two  windings,  making  three  terminal  connections 
for  the  coil.  The  switch  and  coil  are  usually  mounted  as  a  unit  on  the 
dash.  The  collector  brush  on  the  magneto  is  connected  to  the  switch 
on  the  coil.  There  is  also  a  connection  from  the  switch  in  the  coil 
back  to  the  insulated  contact  point  on  the  interrupter  and  another 
connection  from  the  primary  winding  of  the  coil  back  to  a  grounded 
binding  post  on  the  magneto  frame.  The  secondary  terminal  of  the 
coil  is  connected  to  the  central  post  on  the  distributor.  This  makes 

four  connections  when  the  switch  is 
on  the  coil,  although  there  are  really 
only  three  coil  connections.  When 
a  battery  is  used  for  starting  pur- 
poses, another  connection  is  added  to 
the  switch,  and  sometimes  two  if  the 
one  side  of  the  battery  is  not  grounded 
directly. 

The  condenser  may  be  placed  in 
the  coil  box  or  it  may  be  built  in  the 
magneto.  The  switch  may  be  placed 
in  series  with  the  connection  from  the 
armature  to  the  coil  and  interrupter, 
as  shown,  or  it  may  be  arranged  to 
ground  the  armature  current  per- 
manently so  as  to  short  circuit  the 
current  from  the  coil  and  interrupter, 
In  this  latter  connection,  closing  the 
switch  cuts  off  the  ignition  current,  while  opening  the  switch  permits  the 
ignition  to  operate.  A  safety  gap  is  also  provided,  either  at  the  coil  or 
at  the  magneto. 

104.  Dual  Ignition  Systems. — The  majority  of  the  low  tension  mag- 
netos of  the  type  just  described  are  provided  with  an  arrangement  for 
using  battery  current  for  starting  purposes  when  the  magneto  current 
is  small,  due  to  the  low  rotative  speeds.  The  batteries  can  also  be  used 
for  continuous  running  in  cases  of .  emergency,  although  the  life  of  the 
batteries  in  this  case  is  usually  short  because  of  the  long  contact  at  the 
interrupter,  which  wastes  the  battery  current.  The  connections  at 
the  switch  are  usually  made  so  that  when  the  battery  is  used,  the  inter- 
rupter is  in  series  between  the  battery  and  the  coil;  then  the  spark  is 
induced  by  the  interruption  of  the  battery  current  through  the  coil. 


FIG. 


187. — Splitdorf   low-tension   mag- 
neto, model  T. 


thus  rendering  them  inoperative. 


THE  LOW-TENSION  MAGNETO 


153 


In  some  of  the  dual  systems,  the  switch  is  provided  with  a  push-button 
operating  a  vibrator  or  interrupter  in  the  battery  circuit,  so  that  a 
spark  can  be  produced  without  turning  the  engine.  This  enables  the 
operator  to  start  the  engine  on  the  spark  if  there  is  an  explosive  charge 
in  the  cylinder. 

105.  Splitdorf  Low -tension  Dual  Ignition  System  with  Type  T 
Magneto. — The  Splitdorf  low-tension  magneto  ignition  system  is  a 
typical  dual  ignition  system  of  the  interrupted  shunt  current  type. 
Figure  187  shows  the  model  T  magneto  and  Fig.  188  the  circuit  wiring  of 
this  magneto  with  the  typical  box  type  induction  coil  which  is  mounted 
on  the  dash.  The  magneto  is  of  the  armature  wound  type  having 


CELLS 


TO    SPARK    PLUGS 


SAFETY 


SWITCH 


INSULATED  TERMINAL  OH    BREAKER 
BOX  COVER  WITH    BRUSH  ON  INSIDE 
WHICH  MAKES   RUBBING    CONTACT 
WITH    INSULATED  BUTTON  ON   ENQ 
OF  ARMATURE    SHAFT. 


FIG.  188. — Wiring  diagram  of  Splitdorf  low-tension  dual  ignition  system. 

a  single  winding.  The  switch  on  the  coil  box  has  three  positions,  "Off," 
"  Battery, "  and  "  Magneto. "  Figure  188  shows  the  switch  dotted  in 
on  the  "Magneto"  position.  The  armature  current  is  led  from  the  col- 
lector brush  A,  which  is  mounted  in  the  breaker  cap  and  which  rubs 
on  an  insulated  button  on  the  end  of  the  armature  shaft  extending 
through  the  cam,  to  the  coil  box  terminal  A,  and  to  the  lower  right  switch 
button  as  indicated  by  the  arrows.  From  there,  the  current  has  two 
paths  back  to  the  magneto  ground.  One  path  is  by  the  way  of  No.  2 
terminal  over  the  breaker  points  which  are  normally  closed;  the  other, 
through  the  primary  winding  of  the  coil  to  the  grounded  No.  3  magneto 
terminals.  With  the  contacts  closed,  practically  all  of  the  primary 


154 


AUTOMOTIVE  IGNITION  SYSTEMS 


current  will  flow  across  the  breaker  points,  owing  to  the  fact  that  the 
resistance  is  much  less  than  that  through  the  primary  coil  winding. 
When  the  points  open,  this  path  is  broken  and  there  will  be  a  sudden 
rush  of  current  through  the  primary  winding  of  the  coil.  The  action 
of  the  primary  current  combined  with  the  discharge  from  the  con- 
denser induces  a  high-tension  current  in  the  secondary  winding  of  the 
coil.  This  high-tension  current  is  directed  to  the  proper  plug  by  the 
distributor  on  the  magneto.  A  safety  gap  is  provided  on  the  top  of 
the  coil  box. 

With  the  switch  on  the  " Battery"  position  the  magneto  is  discon- 
nected and  the  dry  cells  connected  to  the  primary  circuits.  When 
the  system  is  operating  on  the  batt;ery,  the  coil  and  the  breaker  are 
in  series  and  the  system  operates  as  an  interrupted  primary  current 

system.  The  secondary  circuit  will 
be  the  same  as  when  operating  on  the 
magneto,  namely,  from  the  high-ten- 
sion terminal  on  the  coil  to  the  dis- 
tributor, to  the  plug,  to  the  ground, 
and  returning  to  the  secondary  wind- 
ing over  the  primary  wire  connected 
to  No.  3  grounded  terminal. 

The  condenser  is  mounted  in  the 
coil  and  is  connected  so  as  to  protect 
both  the  magneto  interrupter  points 
and  the  push-button  contacts  on  the 
switch. 

The  push-button  contacts  are  in 
the  primary  circuit  in  series  with  the 
coil  and  are  normally  closed.  When 
.the  switch  is  thrown  on  " Battery" 
position  and  the  breaker  points  are  closed  (which  they  normally  are 
when  the  engine  is  at  a  standstill),  the  primary  circuit  will  be  completed 
and  the  coil  magnetized  by  current  from  the  dry  cells.  If  the  push-button 
is  pressed  and  the  contacts  opened,  the  primary  current  will  be  interrupted, 
causing  a  sudden  demagnetizing  of  the  coil  and  creating  a  secondary  spark 
in  the  cylinder  which  is  lined  up  to  fire  in  accordance  with  the  position  of  the 
distributor  arm.  If  the  cylinder  should  contain  a  combustible  mixture,  it  is 
possible  that  a  spark  caused  in  this  manner  would  ignite  the  mixture  and 
create  sufficient  explosive  pressure  to  kick  the  engine  over,  causing  it  to  start 
without  the  usual  cranking. 

106.  Remy  Inductor  Type  Magneto.— The  .Remy  magneto,  model 
RL,  as  shown  in  Fig.  189,  is  a  typical  low-tension  magneto  of  the  inductor 
type.  Figure  190  shows  the  inductor  and  coil,  while  Fig.  191  shows  the 
coil  and  the  shaft  in  their  places  with  respect  to  the  pole  pieces,  the  mag- 


FIG.   189. — Remy  magneto,  model  RL.j 


THE  LOW-TENSION  MAGNETO 


155 


nets  and  the  shaft  bearings  having  been  removed.  The  two  wing-shaped 
inductors  are  mounted  on  a  steel  shaft  and  are  revolved  on  either  side 
of  the  stationary  coil.  Figure  192  shows  the  path  of  the  magnetism 
during  one  complete  revolution  of  the  inductor. 

When  the  inductors  are  in  the  horizontal  position,  the  flux  enters 
one  inductor,  makes  a  right-angled  turn,  passes  along  the  shaft  and 
through  the  coil  to  the  other  inductor  and  then  to  the  other  pole  piece. 
In  this  position  the  same  condition  exists  as  when  an  armature  of  the 


FIG.  190.- 


-Remy  inductors  and  stationary 
coil. 


FIG.  191. — Remy    inductor    shaft    and 
coil  assembled  in  pole  pieces  and  base. 


shuttle  type  is  in  the  horizontal  position.  When  the  inductors  are  re- 
volved to  the  vertical  position,  the  flux  passes  from  one  pole  piece  direct^ 
across  through  the  inductors  to  the  other  pole  piece,  and  there  is  no  flux 
through  the  coil.  This  change,  therefore,  produces  a  voltage  in  the  coil 
winding.  The  outer  ends  of  the  inductors  are  of  such  length  that  when 
they  are  in  the  vertical  position,  they  offer  a  direct  path  from  one  pole 
piece  to  the  other,  but  when  they  are  horizontal,  the  flux  must  enter  the 


ABODE 

FIG.  192. — Path  of  magnetic  flux  through  Remy  inductor  during  one  revolution. 

one  inductor,  pass  through  the  center  of  the  coil,  and  out  through  the 
other  inductor. 

This  magneto  will  produce  two  current  waves  per  revolution  in  the 
same  manner  as  the  shuttle  type.  The  current  produced  is  also  an  alter- 
nating current  as  the  direction  of  the  flux  through  the  coil  is  reversed 
each  180°  of  revolution  of  the  shaft.  Due  to  the  design  of  the  parts, 
the  current  wave  has  an  abrupt  rise  and  fall  with  an  almost  flat  top, 
making  possible  a  large  timing  range  (35°)  with  practically  the  same 


156 


AUTOMOTIVE  IGNITION  SYSTEMS 


intensity  of  spark.  This  magneto  is  used  for  jump-spark  ignition,  the 
low-tension  current  generated  in  the  coil  being  used  with  a  circuit  breaker 
and  a  step-up  transformer  coil.  The  secondary  current  from  the  trans- 
former is  led  to  a  distributor  on  the  magneto  and  is  there  distributed  to 
the  different  plugs  of  the  engine.  The  circuit  breaker,  Fig.  193,  is 
mounted  on  the  magneto  and  operated  by  a  cam  on  the  end  of  the  arma- 

If  Engine  Misses  with  Spark  Retarded  at  Slow  Speed 
Adjust  the  Contact  Screw  out  a  few  Notches 

To  Adjust  Contact  Screw  If  Engine  Misses  with  Spark  Advanced  at  High  Speed 

Spring  out  Adjust  the  Contact  Screw  in  a  few  Notches 

umb  Screw 


FIG.   193. — Circuit  breaker  of  Remy  magneto. 

ture  shaft,  the  cam  being  mounted  so  as  to  break  the  circuit  in  proper 
relation  to  the  position  of  the  armature  for  maximum  current.  The 
condenser,  Fig.  194,  is  mounted  in  the  arch  of  the  magnets  and  is  con- 
nected directly  across  the  breaker  points. 

Figure  195  shows  an  external  wiring  diagram  of  the  model  RL  magneto 

with  type  LE  switch  and  coil,  while 
Fig.  196  shows  a  diagram  of  the  in- 
ternal circuits.  The  lettering,  R,  Y, 
and  G,  on  the  coil  indicates  the  color 
of  the  wire  intended  by  the  manufac- 
turer to  be  connected  to  that  terminal. 
The  wiring  from  the  coil  to  the  magneto 
is  connected  as  follows: 

Red  R  wire  goes  to  ground  bind- 
ing post  on  timer  end  bearing. 

Yellow  Y  wire  goes  to  contact  screw 
post  on  circuit  breaker. 

Green  G  wire  goes  to  insulated  screw  post  on  the  timer  end  bearing. 

Timing. — For  timing  this  magneto,  the  engine  should  be  turned  over 

with  the  crank  until  No.  1  piston  reaches  top  dead  center  on  compression 

stroke.     The  timing  button  at  the  top  of  the  distributor  should  be  pressed 

in  and  the  magneto  shaft  turned  until  the  plunger  of  the  timing  button 


FIG.    194. — Condenser  for  Remy  model 
RL  magneto. 


THE  LOW-TENSION  MAGNETO 


157 


is  felt  to  drop  into  the  recess  on  the  distributor  gear.  With  the  magneto 
in  this  position  it  should  be  coupled  to  the  engine.  No  attention  should 
be  paid  to  the  circuit  breaker  when  coupling  or  setting  gears  as  the 
breaker  is  automatically  bought  into  the  correct  position,  and  the  dis- 


PUSH  BUTTON 
LET      SWITCH  Jc  Con. 


uunuu 


FIG.   195. — External  wiring  diagram  of  Remy  magneto,  model  RL. 

tributor  segment  is  in  contact  with  No.  1  terminal.     This  No.  1  terminal 
is  plainly  marked  on  the  distributor. 

107.  The  Ford  Ignition  System. — The  Ford  magneto  may  be  classed 
as  a  high-frequency,  alternating  current  magneto  of  the  inductor  type. 


INDUCTION 
COIL 


BAT. 

SWITCH 

(SWITCH  SHOWN  DOTTED 
ON  BAT.  AND  MAG.  Positions' 


DRY     CELLS 

FIG.   196. — Internal  circuit  diagram  of  Remy  magneto,  model  RL. 

It  serves  merely  as  the  source  of  primary  current  for  an  ordinary  vibrating 
coil  type  of  ignition  system.     The  construction  of  the  magneto  is  shown 
in  Fig.  197  and  Fig.  198,  while  the  wiring  diagram  is  shown  in  Fig.  199. 
The  stationary  and  revolving  elements  are  interchanged  from  the 


158 


AUTOMOTIVE  IGNITION  SYSTEMS 


customary  relation.  The  armature  coils  are  stationary  and  the  magnets 
revolve.  The  armature  consists  of  16  coils  which  are  attached  to  a 
stationary  supporting  disc  in  the  flywheel  housing.  An  equal  number  of 


Magneto  Coil  S 

Copper  Wire 

End  of  Ribbon  1 
Grounded  Here  J 

ToCoil 
Magneto  Coil  Support 


FIG.  197. — The  Ford  magneto. 

permanent  magnets  of  the  horseshoe  or  V  type  are  secured  to  the  flywheel 
through  non-magnetic  studs.     The  magnets  revolve  with  the  flywheel  at  a 


TO  MAGNETO  TERMINAL 
ON  COIL  BOX. 


MAGNETO  CONTACT    ON 
FLYWHEEL   HOUSING 


COILS 


COIL- PLATE  BOLTED 
ON  REAP  END  or. 

CRANK -CASE . 


FIG.  198. — Diagram  showing  scheme  of  Ford  magneto. 

distance  of  ^£2  m-  from  the  coils.  The  North  poles  of  two  adjacent 
magnets  are  fastened  together,  likewise  the  next  pair  of  South  poles. 
When  a  pair  of  North  poles  is  in  front  of  the  core  of  one  of  the  coils, 


THE  LOW-TENSION  MAGNETO 


159 


160 


AUTOMOTIVE  IGNITION  SYSTEMS 


VIBRATO)? 
CONTACTS 
ADJUSTING  --< 


CONDCfiSCfiL 


TO  TIME* 


the  magnetic  flux  will  flow  in  through  the  core,  through  the  supporting 
coil  plate,  and  out  through  the  core  of  the  adjacent  coils  to  the  South 
poles  as  shown  in  Fig.  198.  When  the  flywheel  makes  ^{Q  revolution, 
this  flow  is  reversed.  Thus,  16  current  waves  are  generated  per  revolu- 
tion of  the  flywheel.  The  coils  are  all  connected  in  series  with  one  end 
of  the  winding  grounded  and  the  other  end  connected  to  an  insulated 
binding  post  on  the  outside  of  the  flywheel  housing.  This  post  is  con- 
nected to  all  four  induction  coils  through  a  contact  plate  in  the  bottom 
of  the  coil  box.  The  other  ends  of  these  coils  are  connected  to  the  four 
posts  of  the  timer  mounted  on  the  front  end  of  the  camshaft.  Since  one 
end  of  the  magneto  winding  is  grounded,  and  since  the  timer  completes 
the  circuit  to  the  ground  from  each  induction  coil  in  proper  order,  it 
follows  that  the  magneto  current  will  pass  through  whichever  induction 

coil  is  grounded  at  the  timer.  The  induc- 
tion coils  are  of  the  ordinary  double  wound 
induction  type  with  vibrators  to  interrupt 
the  primary  current  from  the  magneto.  A 
diagram  of  the  Hienze-Ford  coil  is  shown 
in  Fig.  200.  The  secondary  of  each  coil 
has  a  direct-  connection  to  the  plug  of  one 
of  the  cylinders  with  a  grounded  return. 

108.  Timing  the  Ford  Ignition  System. 
.The  magneto  is  quite  unlike  those  pre- 
viously described  in  that  the  current  waves 
&K  of  h|gh  ^equency  and  are  not  all  used 
for  ignition.  The  magneto  itself  does  not 
have  to  be  timed  to  the  engine.  The  alternations  of  the  magneto  current 
are  frequent  enough  to  cause  only  a  slight  variation  in  the  instant  of  igni- 
tion as  affected  by  the  periods  of  no  current.  The  length  of  contact  in 
the  timer  is  sufficient  to  overlap  from  one  current  wave  to  the  next.  In 
case  the  magnet  is  in  a  position  where  no  current  is  generated  when  the 
timer  first  makes  contact,  there  will  be  a  lag  of  a  very  few  degrees  in  the 
spark  until  the  magneto  has  turned  into  a  position  where  it  will  generate 
sufficient  current  to  operate  the  coil.  Due  to  the  shape  of  the  current 
waves,  the  greatest  possible  lag  due  to  this  cause  is  probably  not  more  than 
5°  on  the  engine  crankshaft.  The  actual  timing  of  this  system  is  all 
done  at  the  timer.  The  roller  in  the  timer  is  set  so  that  it  will  be  just 
making  contact  with  the  timer  segment  of  cylinder  No.  1  when  the  piston 
in  that  cylinder  is  %  in.  below  top  dead  center  on  the  working  stroke 
and  the  spark  control  lever  on  the  steering  wheel  is  fully  retarded. 


^  MAGNETO 

T'MRU  SWITCH. 


Fl°- 


20F°or7?ndauc?Sn 


CHAPTER  VII 
MODERN  HIGH-TENSION  MAGNETOS— ARMATURE  TYPES 

109.  The  High-tension  Magneto. — Under  the  name  of  high-tension  i 
magneto  are  included  all  magnetos  which  generate,  directly  in  the  mag-  ^ 
neto  winding,  a  current  of  sufficiently  high  voltage  for  jump-spark  igni- 
tion without  the  aid  of  a  separate  induction  coil.     The  magneto  winding  » 
contains  both  a  primary  and  a  secondary  winding,  similar  to  the  winding  / 
of  a  non-vibrating  type  induction  coil,  instead  of  the  usual  single  winding 
found  in  the  low-tension  magneto.     In  the  high-tension  magneto  is  also 


BOSCH  HIGH 
TENSION   MAGNETO 


FIG.  201. — Bosch  high-tension  magneto  installation  on  1918  Marmon  engine. 

incorporated  the  interrupter,  the  distributor,  and  the  condenser,  so  that 
the  magneto  contains  within  itself  practically  all  the  essentials  of  a 
complete  ignition  system,  the  only  necessary  outside  parts  being  the 
spark  plugs  and  the  magneto  controlling  switch.  This  applies  to  both 
the  armature  wound  and  the  inductor  type  of  magneto. 

110.  The  Bosch  High-tension  Magneto. — The  Bosch  magneto,  Fig. 
201  and  Fig.  202,  is  a  typical  high-tension  magneto  of  the  armature  wound 
type.  The  armature  or  rotating  element,  Fig.  203,  is  mounted  on  ball 
bearings  supported  in  the  end  housings  and  rotates  between 'the  magnet 
pole  pieces  shown  in  Fig.  204.  The  armature,  a  cross  section  of  which  is 
shown  in  Fig.  205,  consists  of  a  soft  iron  core,  a  primary  winding  of  com- 
paratively few  turns  of  coarse  wire,  a  secondary  winding  of  many  turns 
11  161^ 


162 


AUTOMOTIVE  IGNITION  SYSTEMS 


OIL  CpVER 


HI6M  TENSION 
COUECT0R  &RUSH\ 


ARMATURE  COVER  PLATE 

OIL  HOUE  COyER 
MAGNETO   COUPLING   \ 


DISTRIBUTOR 
HOLOIN6  SPRING 


SAFETY  SPARK 

GAP  HOUS  INS 

COVER 


DRIVING 
BEAR»NS  PUATE 


FIG.  202. — View  of  driving  end  of  Bosch  high-tension  magneto. 


ARMATURE 
DRIVE 


HARD 
RUBBER 


METAL  SLIPRIN6 
SEGMENT 


INTERRUPTER  END 
ARMATURE  COVER  SERV- 
ING ALSO  AS  CONDENSER 
HOUSING 


SECONDARY   LEAD 
\  TO     SLIPRIN6 

DRiVtNG  END 
ARMATURE    COVER 


FIG.  203. — View  of  armature  of  Bosch  DU4  high-tension  magnetos  showing  ball  bearings 
on  armature  shaft,  and  pinion  that  drives  distributor  gear. 


A6NET5 


-POLE 
PIECES 

\ARMATURE 
6ROUND  BRUSH 


BASE  OF  NON- 
MAGNETIC   METAL 


FIG.  204. — Magnets  and  pole  pieces  of  Bosch  magneto. 


MODERN  HIGH-TENSION  MAGNETOS 


163 


of  fine  wire  wound  on  the  outside  of  the  primary,  and  a  condenser. 
The  condenser,  Fig.  206,  is  mounted  in  one  end  of  the  armature  housing 
and  connected  so  as  to  protect  the  interrupter  points,  the  interrupter 
or  circuit  breaker  being  mounted  on  one  end  of  the  armature  shaft  and 
revolving  with  it.  The  cams  for  actuating  the  interrupter  points  are 


SECONDARY  OR  HIGH 
TENSION  W1NDI 


LAMINATED 
ARMATURE  CORE 


INSULATI 


FIG.  205. — Cross  sectional  view  of  Bosch  high-tension  magneto  armature. 

on  the  inside  of  the  interrupter  housing.  This  arrangement  is  the  reverse 
of  that  of  the  usual  low- tension  magneto  which  has  the  cam  on  the  arma- 
ture shaft  and  the  interrupter  in  the  housing.  By  having  the  interrupter, 
the  condenser,  and  the  primary  winding  all  on  the  armature,  the  entire 
primary  circuit  is  thus  contained  in  the  armature,  forming  a  very  com- 


CLIP  FOR  FASTENING  GROUNDED  5IOE 
OF  CONDENSER  TO  INTERRUPTER   END 
OF  ARMATURE     COVER 


FOR  INSULATED1 
INTERRUPTER 
RETAIN  I N6  SCREW 


BRASS    PLATE 

CONNECTION    FOR  INSULATED 
END  OF  PRIMARY  ARMATURE. 
WINDING 


FIG.  206. — Condenser  of  Bosch  DU4  high-tension  magneto. 

pact  and  efficient  unit.  One  end  of  the  primary  winding  is  grounded  on 
the  armature  core,  and  the  live  end  brought  out  to  a  circuit  breaking 
device.  The  grounded  end  of  the  secondary  winding  is  connected  to  the 
live  end  of  the  primary  winding  so  that  one  is  a  continuation  of  the  other. 
The  magneto  armature  core  is  grounded  to  the  magneto  base  by  the 
ground  brush  shown  in  Fig.  207. 


164 


AUTOMOTIVE  IGNITION  SYSTEMS 


During  certain  parts  of  the  rotation  of  the  armature  the  primary 
circuit  is  closed,  and  the  variations  in  magnetic  flux  induce  an  electric 
current  in  the  winding.  When  the  current  reaches  a  maximum,  which 
will  occur  twice  during  each  rotation  of  the  armature,  the  primary  circuit 
is  broken,  and  the  resulting  collapse  of  the  magnetic  field  in  the  armature 


GROUNDING  BRUSH 


GROUND 
CONNECTION  TO 
BASE  PLATE 

GROUNDING   BRUSH 
RETAINING  SPRING 

BASE  PLATE- 


FIG.  207. — Bottom  view  of  magneto  base  plate  showing  ground  brush. 

produces  a  high-tension  current  of  extreme  intensity  in  the  secondary 
winding.  This  current  is  transmitted  to  the  distributor  through  which 
it  passes  to  the  spark  plugs  in  the  cylinders  in  the  proper  order  of  firing. 
The  Bosch  DU4  high-tension  magneto  is  shown  in  Fig.  208,  while  a 
longitudinal  section  and  the  rear  view  with  the  breaker  cover  removed 

are  shown  in  Fig.  209.     Figure  210  is 
a  circuit  diagram  for  the  magneto. 

Magneto  Interrupter. — The  mag- 
neto interrupter  mechanism  is 
mounted  on  a  circular  disc  which  is 
held  rigid  to  the  armature  shaft  by 
the  interrupter  fastening  screw.  The 
relative  position  of  the  interrupter  to 
the  armature  is  fixed  by  a  key  way  in 
the  end  of  the  armature  shaft  which 
is  taper  bored.  As  may  be  seen  in 
Fig.  210,  the  fastening  screw  also 
forms  the  electrical  connection 
between  the  stationary  (insulated) 
half  of  the  interrupter  and  the 
primary  winding  of  the  armature. 

This  fastening  screw  also  makes  connection  with  the  insulated  terminal  of 
the  condenser,  the  other  terminal  of  which  is  grounded  as  are  also  one  end 
of  the  primary  winding  and  the  movable  contact  arm  of  the  interrupter. 
Twice  during  each  revolution  of  the  armature,  the  primary  circuit 
closes  and  opens,  this  being  caused  by  the  fiber  block  on  the  interrupter 


FIG.  208. — Bosch  high-tension  magneto, 
type  DU4. 


MODERN  HIGH-TENSION  MAGNETOS 


165 


lever  striking  the  two  steel  cams  on  the  inside  of  the  interrupter  housing. 
When  the  interrupter  is  not  being  acted  upon  by  the  cams,  the  interrupter 
points  are  normally  held  closed  by  spring  tension;  consequently,  the 
primary  circuit  is  also  closed.  It  is  very  important  in  this  type  of  inter- 
rupter that  the  interrupter  lever  unit  be  very  accurately  balanced  on  its 
pivot  to  insure  proper  opening  and  closing  of  the  points  at  high  rotating 
speeds.  The  interrupter  points  are  made  of  platinum  and  should  be 
adjusted  to  open  .012  in.  to  .015  in.  on  engines  of  normal  compression. 

Principle  of  Operation. — The  function  of  the  interrupter  or  breaker  is 
to  interrupt  the  circuit  of  the  primary  winding  of  the  armature  when  a 


Longitudinal  secton. 

1.  Brass  plate  for  connecting  the  end  of  the 

primary  winding. 

2.  Fastening  screw  for  magneto  interrupter. 

3.  Contact  block  for  magneto  interrupter. 

4.  Magneto  interrupter  disc. 

5.  Long  platinum  screw. 

6.  Short  platinum  screw. 

7.  Flat  spring  for  magneto  interrupter  lever  8. 

8.  Magneto  interrupter  lever. 

9.  Condenser. 

10.  Collecting  ring. 

11.  Carbon  brush. 

12.  Brush  holder  for  same. 

13.  Terminal  piece  for  conducting  bar  14. 

14.  Conducting  bar. 


Rear  end  interrupter  cover  removed. 

15.  Distributor  brush  holder. 

16.  Distributor  carbon  brush. 

17.  Distributor  plate. 

18.  Central  distributor  contact. 

19.  Brass  segment. 

20.  Knurled  nut  on  terminal  stud. 

21.  Steel  segment. 

22.  Dust  cover. 

24.  Knurled  nut  on  grounding  terminal  stud 

25.  Holding  spring  for  distributor  plate  17. 
116b.  Interrupter  housing  and  timing  arm. 

117.  Cover  for  interrupter  housing. 

118.  Conducting  spring  for  grounding  terminal 
stud. 

119.  Holding  spring  for  interrupter  housing  cover . 


FIG.  209. — Construction  of  Bosch  high-tension  magneto,  type  DU4. 

high-tension  spark  is  to  occur  at  the  plug,  the  action  in  the  armature 
being  similar  to  that  of  an  induction  coil.  This  interruption  must  take 
place  when  the  flow  of  current  through  the  primary  winding  is  at  or  near 
its  maximum  value,  which  occurs  twice  per  revolution  when  the  armature 
core  is  approximately  in  a  vertical  position,  as  shown  in  Fig.  210,  the 
same  as  in  the  low-tension  magneto.  In  this  position,  the  corner  of  the 
armature  is  just  leaving  the  corner  of  the  pole  piece  and  the  winding  is 
cutting  the  greatest  number  of  magnetic  lines  of  force.  In  Bosch  magne- 
tos, having  a  variable  spark  advance,  the  interrupter  points  are  timed  to 
open  when  the  corner  of  the  armature  has  left  the  corner  of  the  pole  piece 
about  HQ  in.  with  the  interrupter  housing  in  full  advance  position.  The 


166 


AUTOMOTIVE  IGNITION  SYSTEMS 


MODERN  HIGH-TENSION  MAGNETOS 


167 


timing  lever  may  be  advanced  about  35°;  then,  when  the  interrupter 
housing  is  fully  retarded,  the  armature  has  passed  the  pole  piece  about 
%  in.  Thus  the  best  spark  is  obtained  with  the  interrupter  in  full 
advance  position,  which  is  the  normal  operating  position  at  high  engine 
speeds. 

Figure  211  A,  B,  and  C  shows  the  distribution  of  the  magnetic  flux 
through  the  armature  core  for  various  armature  positions.  |  Owing  to  the 
rotation  of  both  the  primary  and  the  secondary  windings  of  the  armature 
and  the  consequent  cutting  of  the  magnetic  lines  of  force  by  both  windings, 
a  voltage  is  generated  in  both  the  primary  and  secondary  circuits  propor- 
tional to  the  number  of  turns  in  the  two  windings. /"During  the  period  of 
rotation  when  the  magnetic  field  is  passing  through  the  armature  core, 
the  interrupter  points  are  closed,  thus  completing  (by  short  circuiting) 


FIG.  211.— Di 


of  i^^pietic  flux  through  magneto   armature   core  for  various 
positions. 


the  circ™  K'h  the  primary  winding.  The  current  thus  generated 
in  the  pr^BpK^inding  will  flow  around  the  core,  causing  the  core  to 
become  magnetized  in  a  cross^p-ection  as  shown  in  Fig.  212.  At  ap- 
proximately the  instant  when  the  generated  voltage  is  greatest,  the  inter- 
rupter breaks  the  primary  circuit  thus  permitting  the  armature  core  to 
demagnetize  instantly.  This  causes  a  high  voltage  to  be  induced  in  the 
secondary  winding  in  the  same  direction  as  the  generated  voltage.  The 
induced  current  produced  by  the  interruption  of  the  primary  circuit 
lasts  a  very  short  interval  of  time  and,  if  acting  alone,  would  produce  but 
a  single  flash  at  the  spark  plug.  However,  owing  to  the  revolving  of  the 
secondary  winding  in  the  magnetic  field,  a  more  continuous  current  of 
not  so  high  a  voltage  is  generated.  This  generated  voltage  alone  is  not 
sufficient  to  break  down  the  resistance  of  the  gap  in  the  spark  plug,  but 
at  the  instant  the  primary  circuit  is  interrupted,  the  induced  current  is 
sufficient  to  break  down  this  resistance  and  then  the  somewhat  lower  vol- 


168 


AUTOMOTIVE  IGNITION  SYSTEMS 


tage  of  the  generated  current  is  able  to  maintain  the  flow  of  current 
across  the  gap,  thus  producing,  not  an  instantaneous  flash,  but  a  hot  flame 
which  lasts  for  a  considerable  period.  The  heat  produced  by  this  pro- 
longed spark  is  much  more  intense  than  that  produced  by  the  short 
flash  caused  by  the  induced  current. 

Condenser. — The  condenser,  as  in  most  high-tension  armature  type 

I  magnetos,  is  located  in  one  end  of  the  armature.     It  is  connected  in 

parallel   with   the   primary  winding   and   the  interrupter   circuit.     As 

stated  previously,  the  purpose  of  the  condenser  is  to  absorb  the  induced 

I  charge  in  the  primary  winding  and  prevent  the  discharge  of  this  current 

!  across  the  interrupter  points.     The  charge  in  the  condenser  surges  back 

into  the  primary  winding  in  the  opposite  direction  to  that  of  the  primary 


SECONDARY  WIRE 
GROUNDED  TO  PRIMARY 


..INTERRUPTER 

CONTACTS 
NORMALLY    CUOSEO 


FIG.  212. — Diagram  showing  armature  cross-magnetization  due  to 
primary  and  secondajfc  winding. 


•  •urrent  generated  in 


current,  thereby  causing  a  more  rajjjd  demagnetization  of  the  armature 
and,  consequently,  producing  a  higher  voltage  in  the  secondary  winding 
than  would  otherwise  be  obtained. 

In  the  diagram  shown  in  Fig.  210  it  will  be  seen  that  one  end  of  the 
secondary  winding  is  connected  to  the  insulated  end  of  the  primary  wind- 
ing so  that  the  one  forms  a  continuation  of  the  other.  The  other  end  of 
the  secondary  winding  leads  to  the  collector  ring  or  slip  ring  on  which 
slides  a  carbon  brush,  insulated  from  the  magneto  frame.  The  secondary 
current  is  conducted  from  the  brush  to  the. center  distributor  contact 
and  from  there  through  the  carbon  brush  (carried  on  the  distributor  gear 
wheel)  to  the  various  cable  connections  and  spark  plugs  in  their  proper 
order  of  firing.  After  jumping  the  spark  plug  points,  the  current  returns 


MODERN  HIGH-TENSION  MAGNETOS 


169 


through  the  engine  frame  and  the  ground  brush  in  the  base  of  the  mag- 
neto, Fig.  207  and  Fig.  210,  to  the  armature  core  and  back  to  the  begin- 
ning of  the  secondary  winding.  As  in  the  low-tension  armature  type  of 
magneto,  there  are  two  sparks  produced  per  revolution  of  the  armature. 
The  distributor  is,  therefore,  similar  to  that  found  on  the  low-tension 
magneto  and  is  driven  at  similar  speeds.  The  only  difference  is  that  the 
secondary  current  is  received  direct  from  the  armature  instead  of  being 
brought  back  to  the  distributor  from  a  transformer  coil.  The  distributor 
has  as  many  segments  as  there  are  engine  cylinders  and  is  driven  at  one- 
half  the  speed  of  the  crankshaft.  For  a  four-cylinder  engine  the  dis- 
tributor has  four  segments  and  is  driven  at  one-half  the  speed  of  the  arma- 
ture. For  a  six-cylinder  engine  there  are  six  segments,  and  the  distributor 


OIL  WELL  COVER 


SET  SCREW  FOR 
DISTRIBUTOR 
SEAR  SHAFT 


DISTRIBUTOR    BLOCK 
SPRING  CATCH  « 


REFERENCE  POINTS  FOR 
CHANGING  ROTATl 
AND  TIMING 


OIL    GROOVE 
FOR  BALL  BEARING 

FOR  SCREWS  TO 

ATTACH  INTERRUPPTER 

END     PLATE  COVER 

CONTAINING  BALL  RACE 


INTERRUPTER  END  PLATE 


ISTR1BUTOR  BRUSH 
BRUSH  HOLDER 


DISTRIBUTOR  BLOCK 
V/ISPRIN6  CATCH 


DISTRIBUTOR  END  OF  PENCIL 
BRUSH  OR  CONDUCTING  BAR 

DISTRIBUTOR  6EAR 
DISTRIBUTOR  PINION 
BALL  BEARING 

KEY  WAY  TO 
RECEIVE  KEY  Op 
INTERRUPTER 


L  OVERFLOW 


FIG.  213. — Bosch  distributor  gears  showing  markings  for  timing  distributor  with  armature. 

arm  is  driven  at  one-third  the  speed  of  the  armature.  The  relations  of 
magneto  speeds  to  engine  speeds  are  also  the  same  as  for  the  armature 
type  of  low-tension  magnetos.  For  a  four-cylinder  four-stroke  engine 
the  armature  revolves  at  crankshaft  speed.  For  a  six-cylinder  four- 
stroke  engine  the  armature  revolves  at  one  and  one-half  times  crankshaft 
speed.  Likewise,  for  an  eight-  or  twelve-cylinder  engine  a  magneto  of 
this  type  must  be  driven  at  twice  or  three  times  crankshaft  speed, 
respectively,  in  order  to  produce  the  required  number  of  sparks  per 
revolution  of  the  engine. 

Care  should  be  taken  in  assembling  the  magneto  to  get  the  distributor 
gear  timed  correctly  with  the  armature  so  that  the  distributor  brush  will 
be  in  proper  alignment  with  the  distributor  head  segment  when  the  inter- 
rupter points  open  with  the  breaker  housing  in  either  the  advance  or 


170  AUTOMOTIVE  IGNITION  SYSTEMS 

retard  positions.  On  full  advance  position,  the  distributor  brush  should 
be  moving  on  to  the  distributor  head  segment  when  the  interrupter 
contacts  open,  and  should  be  leaving  the  same  segment  when  the  contacts 
open  with  the  breaker  housing  shifted  to  full  retard  position.  Figure 
213  shows  the  punch  markings  on  the  distributor  gears  for  the  purpose  of 
timing  the  distributor  with  the  armature.  For  a  magneto  having  clock- 
wise direction  of  rotation,  the  punch  mark  "C"  on  the  distributor  gear 
should  mesh  with  the  punch  mark  on  the  armature  gear,  while  in  the  case 
of  a  magneto  with  anti-clockwise  rotation,  the  gears  should  be  meshed  so 
that  the  punch  mark  "A"  will  mesh  with  the  punch  mark  on  the  arma- 
ture. The  direction  of  armature  rotation  is  usually  indicated  by  an  arrow 
stamped  on  the  magneto  housing  near  the  driving  end  of  the  armature 
shaft. 

The  Safety  Spark  Gap. — In  order  to  protect  the  insulation  of  the 
armature  and  of  the  current-conducting  parts  against  excessive  voltage, 
a  safety  spark  gap  of  about  %Q  in.  is  provided  as  shown  in  Fig.  210. 
The  current  will  pass  through  this  gap  in  case  a  cable  connection  to  one 
of  the  spark  plugs  becomes  disconnected  while  the  magneto  is  in  opera- 
tion, or  if  the  electrodes  on  the  spark  plugs  are  too  far  apart.  The 
secondary  current  should  not  be  permitted  to  jump  the  safety  gap  for 
any  length  of  time  as  the  continued  discharge  of  the  current  over  the 
safety  gap  is  liable  to  damage  the  magneto  winding  and  the  condenser. 

The  Magneto  Grounding  Switch. — In  order  to  cut  off  the  ignition 
without  damaging  the  windings,  the  primary  current  must  be  short 
circuited  so  that  it  will  not  be  interrupted  when  the  interrupter  points 
open.  This  is  arranged  for  by  connecting  a  wire  from  the  insulated 
terminal  on  the  breaker  cover,  to  a  simple  ground  switch  which  has  two 
terminals,  one  of  which  connects  to  the  engine  or  chassis  frame.  The 
terminal  on  the  breaker  cover  is  connected  by  a  brush  to  the  insulated 
half  of  the  interrupter,  so  that  when  the  switch  is  closed  the  primary 
current  is  short  circuited  through  the  switch  and  ground  and  the  magneto 
ceases  to  generate  sufficient  voltage  in  the  secondary  winding  to  jump 
the  spark  plug  points,  thus  preventing  ignition. 

111.  The  Bosch  High-tension  Dual  Ignition  System. — In  the  Bosch 
high-tension  dual  ignition  system,  the  standard  type  of  Bosch  magneto 
is  used  with  the  application  of  two  timers  or  interrupters.  The  parts  of 
the  regular  current  interrupter  are  carried  on  a  disc  that  is  attached  to 
the  armature  and  revolves  with  it,  the  rollers  or  segments  that  serve  as 
cams  being  supported  on  the  interrupter  housing.  In  addition,  the 
magneto  is  provided  with  a  steel  cam  which  is  built  into  the  interrupter 
disc,  and  has  two  projections.  This  cam  acts  on  a  lever  supported  by 
the  interrupter  housing,  the  lever  being  connected  in  the  battery  circuit 
so  that  it  serves  as  a  timer  to  control  the  flow  of  battery  current.  These 
parts  may  be  seen  in  Fig.  214.  A  non- vibrating  transformer  coil  is 
used  with  the  battery  current  to  produce  the  necessary  voltage. 


MODERN  HIGH-TENSION  MAGNETOS 


171 


It  is  obvious  that  the  sparking  current  from  the  battery  and  from 
the  magneto  cannot  be  led  to  the  spark  plugs  at  the  same  time,  so  a 
further  change  from  the  magneto  of  the  independent  form  is  found 
in  the  removal  of  the  direct  connection  between  the  collecting  ring  and 
the  distributor.  The  collecting  ring  brush  shown  in  Fig.  215  as  No.  3  is  con- 
nected to  the  switch,  and  a  second  wire  leads  from  the  switch  to  the 
central  terminal  on  the  distributor.  When  the  engine  is  running  on  the 
magneto,  the  sparking  current  that  is  induced  in  the  secondary  armature 
winding  flows  to  the  distributor  by  way  of  the  switch  contacts.  When  the 
engine  is  running  on  the  battery,  the  primary  circuit  of  the  magneto  is 


GH    TENSION    CONNECTION 


FIG.  214.- — Bosch  dual  magneto  showing  magneto  interrupter  and  battery  timer. 

grounded,  and  there  is,  therefore,  no  production  of  sparking  current  by 
the  magneto.  The  sparking  current  from  the  coil  then  flows  to  the  cen- 
tral distributor  connection.  It  will  be  seen  that  the  only  parts  of  the 
magneto  and  battery  circuits  used  in  common  are  the  distributor  and 
the  spark  plugs. 

The  Bosch  Dual  Coil. — The  Bosch  dual  coil  used  in  the  dual  system 
is  contained  in  a  cylindrical  housing  with  a  brass  casting  on  one  end, 
the  flange  of  which  serves  to  attach  the  coil  to  a  dashboard  or  other 
part.  The  coil  is  provided  with  a  key  and  lock,  by  which  the  switch 
may  be  locked  when  in  the  "OFF"  position.  This  is  a  point  of  great 
advantage,  as  it  makes  it  unlikely  that  the  switch  will  be  left  thrown 


172 


AUTOMOTIVE  IGNITION  SYSTEMS 


to  the  battery  position  when  the  engine  is  brought  to  a  stop.  The 
absence  of  such  an  attachment  is  responsible  in  a  large  measure  for  the 
accidental  running  down  of  the  battery.  This  locking  device  also 
prevents  the  unauthorized  operation  of  the  engine.  The  parts  of  the 
coil  are  shown  in  Fig.  216.  In  addition  to  the  housing  and  end  plate, 
the  parts  consist  of  the  coil  itself,  the  stationary  switch  plate,  and  the 
connection  protector. 

When  the  engine  is  running  on  battery  ignition,  a  single  contact 
spark  is  secured  at  the  instant  when  the  battery  interrupter  breaks 
its  circuit,  and  the  intensity  of  this  spark  permits  efficient  operation 
of  the  engine  on  the  battery  system. 


Battery. 

Secondary   to  Dist. 
May.  See,  fe  Snitcfi. 
Meg.  Grounding  Wire. 
Battery  Circuit  Breaker 


FIG.  215. — Wiring  diagram  for  Bosch  dual  ignition  system. 

Starting  on  the  Spark. — For  the  purpose  of  starting  on  the  spark, 
a  vibrator  may  be  cut  into  the  coil  circuits  by  turning  the  button  that 
is  seen  on  the  coil  body  in  Fig.  215  and  Fig.  216.  Normally,  this  vibra- 
tor is  out  of  circuit,  but  the  turning  of  the  button  places  it  in  the 
battery  primary  circuit.  A  vibrator  spark  of  high  frequency  is  thus 
produced. 

It  will  be  found  that  the  distributor  on  the  magneto  is  then  in  such 
a  position  that  this  vibrator  spark  is  produced  at  the  spark  plug  of 
the  cylinder  that  is  performing  the  power  stroke.  If  a  combustible 
mixture  is  present  in  this  cylinder,  ignition  will  result  and  the  engine 
will  start. 

Connections. — In  the  wiring  diagram  of  this  system,  as  shown  in 
Fig.  215,  it  will  be  noted  that  while  the  independent  magneto  requires 


MODERN  HIGH-TENSION  MAGNETOS 


173 


but  one  switch  wire  in  addition  to  the  cables  between  the  distributor 
and  spark  plugs,  the  dual  system  requires  four  connections  between 
the  magneto  and  the  switch;  two  of  these  are  high  tension,  consisting 
of  wire  No.  3  by  which  the  high-tension  current  from  the  magneto  is 
led  to  the  switch  contact,  and  wire  No.  4  by  which  the  high-tension 
current  from  either  the  magneto  or  the  coil  goes  to  the  distributor.  Wire 
No.  1  is  a  low-tension  wire  conducting  the  battery  current  from  the 
primary  winding  •  of  the  coil  to  the  battery  interrupter.  Low-tension 
wire  No.  2  is  the  grounding  wire  by  which  the  primary  circuit  of  the 
magneto  is  grounded  when  the  switch  is  thrown  to  the  "OFF"  or  to  the 
" Battery"  position.  Wire  No.  5  leads  from  the  negative  terminal 
of  the  battery  to  the  coil,  the  positive  terminal  of  the  battery  being 
grounded  by  wire  No.  7.  Wire  No.  6  is  a  second  ground  wire  connect- 
ed to  the  coil  terminal. 


FIG.  216. — Parts  of  Bosch  dual  coil. 

112.  The  Bosch  High-tension  Magneto,  Type  NU4.— The  Bosch 
magneto,  type  NU4,  Fig.  217,  is  of  the  high-tension,  armature  wound 
type  and  is  suitable  only  for  four-cylinder,  four-cycle  engines  of  the 
automobile  type,  rated  at  or  under  30  horsepower.  A  distinct  feature 
of  this  magneto  is  the  absence  of  the  usual  gear-driven  distributor,  this 
being  incorporated  in  the  form  of  a  double  high-tension  slip  ring  mount- 
ed on  one  end  of  the  armature  shaft  as  shown  in  Fig.  218.  The 
magneto  interrupter,  Fig.  219,  is  the  same  as  that  used  in  the  ordinary 
Bosch  independent  high-tension  magneto. 

A  circuit  diagram  of  this  magneto  is  shown  in  Fig.  220A.  It  will 
be  noted  that  the  circuit  of  the  primary  winding  is  the  same  as  for  the 
Bosch  DU4  shown  in  Fig.  210.  The  secondary  winding,  however, 
is  not  connected  to  the  primary,  its  two  ends  being  connected  to  the 
two  metal  segments  in  the  slip  ring  mounted  on  the  armature  just  in- 
side of  the  driving  shaft  end  plate  of  the  magneto.  The  slip  ring  has 


174 


AUTOMOTIVE  IGNITION  SYSTEMS 


two  grooves,  each  containing  one  of  the  two  metal  segments.  These 
segments  are  set  diametrically  opposite  on  the  armature  shaft,  that 
is,  180°  apart,  and  are  insulated  from  each  other  as  well  as  from  the 
armature  core  and  magneto  frame. 


FIG.  217. 


FIG.  218. 


FIG.  217. — Bosch  high-tension  magneto,  Type  NU4. 

FIG.    218. — Distributor  on  Bosch  "NU4"  magneto  showing  position  of  the  carbon 
brushes  with  relation  to  the  slip  ring. 

The  four  slip  ring  brushes  which  collect  the  secondary  current  are 
supported  by  two  double  brush  holders,  one  on  each  side  of  the  driv- 
ing shaft  end  plate,  each  holder  carrying  two  brushes  so  arranged  that 
each  brush  bears  against  the  slip  ring  in  a  separate  groove.  Upon 
rotation  of  the  armature,  the  metal  segment  in  one  slip  ring  groove 


FIG.  219. — Interrupter  end  of  Bosch  "NU4"  magneto. 

makes  contact  with  a  brush  on  one  side  of  the  magneto  at  the  same 
instant  that  the  metal  segment  in  the  other  slip  ring  groove  comes  into 
contact  with  a  brush  on  the  opposite  side  of  the  magneto.  The  marks 
"1"  and  "2"  appearing  in  white  on  both  brush  holders  indicate  pairs 
of  brushes  receiving  simultaneous  contact,  those  marked  "1"  consti- 
tuting one  pair,  and  those  marked  "2,"  the  other. 


MODERN  HIGH-TENSION  MAGNETOS 


175 


113.  Timing  the  Bosch  Magneto,  Type  NU4. — From  the  wiring 
diagram  it  is  important  to  note  that  since  two  of  the  four  slip  ring  brushes 
make  contact  simultaneously  and  each  is  connected  by  cable  to  the 


SPARK   PLUGS 


MAGNETS 


PLATINUM  INTERRUPTER 
POINTS  SHOULD 


INSULATED    INTERRUPTER 
CONTACT 


STEEL    CAM 


NTERRUPTER  COVER 


FIG.  220A. — Circuit  diagram  of  Bosch  "NU4"  high-tension  magneto. 

spark  plug  in  one  of  the  cylinders,  the  secondary  circuit  always  includes 
two  plugs,  the  sparks  occurring  in  two  cylinders  at  the  same  time, 
namely,  cylinders  Nos.  1  and  4  or  Nos.  2  and  3.  Only  one  of  these 
sparks,  if  properly  timed,  will  cause 
ignition  since  in  a  four-cylinder  engine, 
when  No.  1  cylinder  is  under  compres- 
sion ready  for  ignition,  No.  4  piston 
is  finishing  its  exhaust  stroke  and  the 
cylinder  contains  nothing  but  burned 
exhaust  gases.  The  same  relation 
exists  when  each  cylinder  is  ready  for 
ignition,  the  other  cylinder  in  which 
the  spark  occurs  containing  non-com- 
bustible exhaust  gases.  Care  should 
be  taken  in  timing  this  type  of  mag- 
neto so  that  when  fully  retarded  the 
spark  will  not  occur  in  the  dead 
cylinder  after  the  intake  valve  has 
opened,  which  is  usually  a  crank  angle  of  about  8°  to  10°  past  upper 
dead  center.  The  platinum  interrupter  points  should  be  adjusted  to 
open  .015  in.,  while  the  spark  plugs  should  be  adjusted  to  a  gap  of  .020 
in.  to  .030  in.,  or  the  thickness  of  a  worn  dime. 


FIG.    220B. — Bosch    high-tension 
neto,  type  B. 


mag- 


176 


AUTOMOTIVE  IGNITION  SYSTEMS 


Bosch  High-tension  Magneto,  Type  B. — The  Bosch  type  B  magneto, 
Fig.  220B,  is  a  late  product  of  the  Bosch  Magneto  Company  and  is 
fitted  to  many  engines  made  later  than  the  spring  of  1920.  The  type  B 
magneto  is  equal,  electrically  and  mechanically,  to  any  of  the  Bosch 
types  which  have  preceded.  Moreover,  it  is  simple  in  construction 


Z    L    K 


M    V    N    L 


A.  Armature 

B.  Condenser^ 

C.  Distributor  rotor 

D.  Collector  ring 
H.  Distributor  gear 

I.  Distributor  rotor  shaft 

J.  Shaft  adapter  head 

K.  Distributor  block 

L.  Terminal  nut 

M.  Interrupter  disc 

N.  Contact  block 

O.  Interrupter  fastening  screw 

Q.  Rear  end-plate 

T.  Interrupter  housing 

V.  Interrupter  cam 

W.  End  cap 

X.  End     cap    contact    spring 

with  brush 

Y.  Holding  post  spring 
Z.  Distributor  brush 


FIG.  220C. — Vertical  section  of  Bosch  type  B  magneto. 

and  can  be  manufactured  and  kept  in  adjustment  very  easily.  The 
frame  of  this  magneto  is  made  of  cast  aluminum  and  includes  the  magneto 
base  and  the  shaft  end  plate.  The  armature  and  the  interrupter  are  of 

the  regular  Bosch  construction. 

The  distributor,  instead  of  being 
mounted  over  the  interrupter  hous- 
ing, is  located  at  the  drive  end  of  the 
magneto.  It  is  mounted  at  the  top  of 
a  vertical  shaft  driven  by  spiral  gears 
from  the  armature  shaft  as  shown  in 
Fig.  220C.  This  construction  gives  a 
vertical  distributor  similar  to  those  on 
battery  ignition  units. 

This  magneto  is  also  made  up  in  a 
special  form  for  tractor  use  and  is 
known  as  the  type  BT,  which  is  in 
all  respects  similar  to  the  type  B 
magneto  except  that  it  is  provided  with  the  Bosch  adjustable  impulse 
coupling  enclosed  in  a  dust-  and  waterproof  case. 

114.  The  Eisemann  High-tension  Magneto,  Type  G4. — The  Eise- 
mann  high-tension  magneto,  type  G4,  Fig.  221,  is  typical  of  the  various 
models  of  the  Eisemann  magneto.  It  is  made  in  two  types  known  as 
G4,  I  Edition,  and  G4,  II  Edition.  The  principal  differences  between 


FIG  221. — Eisemann  high-tension  mag- 
neto, Type  G4,  II  edition. 


MODERN  HIGH-TENSION  MAGNETOS 


177 


DISTRIBUTOR  PLATE 


CABLE  FOR  CUTTING 
OFF  IGNITION 


DISTRIBUTOR 
CARBONS 


END  CAP 

SETTING  SCREW 
DISTRIBUTOR  DISC     jSETTING  MARKS 


CARBON  BRUSH  PICKING  UP  \ 
CURRENT  FROM  COLLECTOR  RING 


COPPER  BRUSH  FOR  SHORT 
CIRCUITING  IGNITION 


FIG.  222. — Principal  parts  of  Eisemann  high-tension  magneto,  type  G4,  I  Edition. 


FIG.  223.  —  Eisemann   magneto,  type  G4,  I  Edition,  with   distributor  removed  showing 
setting  marks  for  timing,  also  method  of  adjusting  interrupter  contacts. 


12 


178 


AUTOMOTIVE  IGNITION  SYSTEMS 


the  two  models  are  in  the  design  of  the  interrupter  mechanism  and  in 
the  construction  of  the  armature  housing. 

In  the  type  G4,  I  Edition,  shown  in  Fig.  222,  the  movable  contact 
of  the  interrupter  is  carried  on  a  flat  spring  instead  of  on  the  usual 
rocking  type  lever.  The  interrupter  points  are  actuated  by  this  spring's 
striking  the  two  fiber  cams  on  either  side  of  the  center  part  of  the  tim- 
ing lever  body.  The  fixed  end  of  the  spring  is  grounded  to  the  magneto 
frame  through  a  grounding  brush  which  bears  on  the  inside  of  the  tim- 
ing lever  body.  In  •  this  type  of  magneto  the  interrupter  platinum 
points  may  be  adjusted  without  removing  the  timer  body  as  shown  in 
Fig.  223.  In  the  type  G4,  II  Edition,  the  usual  form  of  rocking  type 


DISTRIBUTOR    PLATE 

WITH 
WATER-PROOF  CABLE   FASTENINGS 


INDICATOR   POINT 

FOR    SETTING    MAGNETO 

TO  MOTOR 


SETTING 
'MARKS 


WATER- PROOF'ENtf 
CAP  FOR    BREAKER 


MAGNETO  CONTACT 
BREAKER  POINTS 


TIMING  LEVER  BODY 

FIG.  224. — Principal  parts  of  Eisemann  high-tension  magneto,  type  G4,  II  Edition. 

interrupter  is  used,  in  which  the  interrupter  lever  is  actuated  by  two 
steel  segments  or  cams  mounted  on  the  inside  of  the  timing  lever  body 
as  shown  in  Fig.  224.  The  platinum  contacts  in  both  types  of  magnetos 
should  be  adjusted  to  open  .010  in.  to  i014  in. 

The  armature  housing  or  frame  of  the  type  G4,  II  Edition,  consists 
of  the  unit-cast  construction  shown  in  Fig.  225,  whereas  the  1  Edition 
housing  is  built  up  of  several  parts  screwed  together.  This  unit-casting 
is  extremely  rigid,  thus  eliminating  all  danger  of  loosened  screws  or  end 
plates,  due  to  vibration  or  accidental  twisting.  Another  advantage  of 
the  unit-casting  is  the  absence  of  any  joints.  Consequently,  an  abso- 
lutely water-,oil-,  and  dust- tight  protection  is"  provided  for  the  vital  ele- 
ments, such  as  the  winding  and  the  condenser.  The  unit-casting  may 


MODERN  HIGH-TENSION  MAGNETOS  179 

be  bored  out  and  machined  all  in  one  piece,  and  because  of  its  rigidity,  a 
smaller  running  clearance  between  the  armature  and  the  poles  of  the  mag- 
nets can  be  maintained.  This  tends  to  give  increased  magnetic  effici- 
ency and,  as  a  result,  a  much  hotter  spark. 

The  Armature. — The  armature  used  in  the  Eisemann  magneto  is 
shown  in  Fig.  226.     The  armature  core  carries  the  winding  and  is  of 


FIG.  225. — Frame  casting  for  Eisemann  magneto,  type  G4,  II  Edition. 

the  H-shaped  type,  similar  to  that  shown  in  Fig.  205.  On  this  core  are 
wound  a  few  layers  of  medium  sized  copper  wire,  the  beginning  end  of 
which  is  grounded  to  the  armature  core.  The  other  end  of  the  wire  is 
connected  through  the  interrupter  fastening  screw  to  the  insulated  con- 
tact of  the  breaker  mechanism.  Over  this  primary  winding  is  the  second- 


CONDENSER  ARMATURE         COLLECTOR  RING 

WINDING 


FIG.  226. — Armature  for  Eisemann  magneto. 


ary  winding  consisting  of  many  turns  of  very  fine  copper  wire,  the  wire 
itself  being  insulated  its  entire  length  and  the  layers  carefully  insulated 
from  each  other.  A  circuit  diagram  of  the  Eisemann,  type  G4, 1  Edition, 
is  shown  in  Fig.  227.  It  will  be  noticed  that  the  beginning  of  the  secondary 
is  connected  directly  to  the  end  of  the  primary  winding,  and  the  end  is 


180 


AUTOMOTIVE  IGNITION  SYSTEMS 


led  to  the  collector  ring  which  is  mounted  on  the  same  end  of  the  arma- 
ture as  the  interrupter.  The  condenser,  which  is  connected  so  as  to 
protect  the  interrupter  points,  is  mounted  in  the  other  end  of  the  arma- 
ture. 


TO    SPARK     PLUGS 


MAGNETO  GROUNDING 
SWITCH 


GROUND  BRUSH  IN  END  PLATE 

JL   /  PRIMARY 

•~lp  /     .SECONDARY 


CONDENSER 


FASTEh 
INTERRUPTER 


TIMING  LEVER 


END  CAP 


CONTACT  ARM  ACTUATED 
BY    FIBER   CAMS  IN  TH1INO- 
LEVER   HOUSING 

FIG.  227. — Circuit  diagram  of  Eisemann  high-tension  magneto,  type  G4,  I  Edition. 


SAFETY    GAP 
(BETWEEN  M.T.  SLJPRING     GROUND  BRUSH 
AND  SCREW  IN  END  HOUSING) 


Pole  Pieces. — One  of  the  distinct  features  of  the  Eisemann  magneto 
is  the  shape  of  the  pole  pieces,  which  are  wedge-shaped  as  shown  in  Fig. 
228.  These  wedge-shaped  pole  pieces  cause  the  magnetic  lines  of  force 
to  flow  from  the  extremities  of  the  pole  pieces  toward  the  center  of  the 


FIG.  228. — Wedge-shaped  pole  pieces  used  on  older  model  Eisemann  magnetos. 

core.  All  of  the  magnetic  lines  of  force  are  thus  forced  through  the  wind- 
ing of  the  armature  and  are  not  diffused  as  in  the  case  of  the  straight 
pole  pieces  which  are  most  commonly  used.  The  wedge-shaped  pole 
pieces  also  prolong  the  duration  of  maximum  current  in  the  primary 


MODERN  HIGH-TENSION  MAGNETOS 


181 


winding,  when  the  corner  of  the  armature  passes  the  pole  pieces,  thus 
increasing  the  angle  of  spark  range  and  permitting  a  hotter  spark  with 
breaker  in  retard  position.  The  armature,  which  is  always  overlapped 
by  the  pole  pieces,  acts  as  a  keeper  to  the  magnets,  thereby  aiding  in 
preventing  demagnetization  which  is  common  to  magnetos  with  straight 
pole  pieces.  These  pole  pieces  greatly  reduce  the  wear  on  the  coupling 
or  gear  which  drives  the  magneto,  by  preventing  the  sudden  breaking  of 
the  magnetic  field  and  assisting  in  making  the  magneto  gears  noiseless. 

The  Distributor. — By  placing  the  collector  ring  on  the  same  end  of 
the  magneto  as  the  distributor  head,  the  necessity  of  carrying  the  high- 
tension  current  around  the  magneto  by  means  of  brushes  and  conductors 
is  done  away  with.  A  brush  in  the  distributor  plate  carried  straight  down 
to  a  contact  with  the  collector  ring  is  used  and  in  this  manner  the  high- 
tension  current  is  carried  directly  to  the  center  brush  in  the  distributor 

plate.     This    center    brush    in    turn    „ '. , 

makes  contact  with  the  metal  insert 
of  the  distributor  disc.  This  disc  is 
attached  to  the  distributor  gear  and, 
consequently,  rotates  with  it,  so  that 
the  metal  insert  makes  contact  in  rota- 
tion with  each  of  the  outside  carbons 
of  the  distributor  plate,  whence  cur- 
rent is  led  to  the  spark  plugs  by  the 
high-tension  cables. 

The  safety  spark  gap  is  located  in 
the  breaker  end  of  the  magneto  in- 
stead of  in  the  arch  of  the  magnets,  as 
in  the  usual  armature  wound  type 
magneto.  It  consists  of  a  gap  of 
about  %6  m-  between  the  collector  ring  and  the  point  of  a  screw  placed 
in  the  armature  housing,  immediately  behind  the  breaker.  Its  purpose 
is  to  provide  a  by-pass  for  the  high-tension  current,  thereby  protecting 
the  high-tension  winding  against  possible  injury  in  case  a  spark  plug 
cable  should  become  disconnected  or  broken. 

115.  The  Eisemann  High-tension  Dual  Magneto,  Type  GR4. — The 
Eisemann  high-tension  dual  magneto,  known  as  type  GR4,  II  Edition,  is 
shown  in  Fig.  229  and  Fig.  230.  It  is  used  in  conjunction  with  a  battery 
(either  dry  cells  or  storage  battery)  and  either  the  DC  or  the  DCR  type 
coil  shown  in  Fig.  231. 

The  primary  purpose  of  this  system  is  to  give  two  sources  of  ignition 
(magneto  and  battery),  using  one  distributor  and  one  set  of  spark  plugs. 
The  arrangement  consists  essentially  of  a  direct  high-tension  magneto, 
used  in  conjunction  with  a  combined  transformer  coil  and  switch  which 
can  be  mounted  on  the  dash.  This  transformer  coil  is  used  only  in  con- 


FIG.  229. — Eisemann  high-tension  dual 
magneto,  type  GR4,  II  Edition. 


182 


AUTOMOTIVE  IGNITION  SYSTEMS 


nection  with  the  battery,  whereas  the  switch  is  used  in  common  with  both 
the  battery  and  the  magneto. 

The  magneto,  as  may  be  seen  from  Fig.  230,  is  practically  the  same 
as  the  type  G4  independent  magneto  with  two  exceptions,  the  timing  arm 
is  equipped  with  an  extra  separate  contact  breaker  for  the  battery  cur- 
rent, and  the  distributor  is  modified  to  permit  of  its  electrical  separation 
from  the  magneto  armature  when  distributing  the  battery  spark. 


DISTRIBUTOR    PLATE 

WITH 
WATER-PROOF  CABLE   FASTENINGS 


INDICATOR  POINT 

FOR  SETTING. MAGNETO 

TO  MOTOR 


SETTINO 

MARKS 


DISTRIBUTOR 
CARBON    BRUSHES 


CARBOH  BRUSH 

TO  PICK  UP  CURRENT 

FROM  COLLECTOR  RING 


CABLE  CONNECTION 
FOR  CUTTING  OFF  MAGNETO 
IGNITION 


WATER- PHOOF  END 
CAP  FOR   BREAKERS 


WATER-PROOF  NUt 
FOR  BATTERY 
BINDING  POST 


TIMING  LEVER  BODY 


MAGNETO  CONTACT 
BREAKER  POINTS 

FIG.  230. — Principal  parts  of  Eisemann  high-tension  dual  magneto,  type  GR4,  II  Edition. 


This  magneto  may  be  used  with  equally  good  results  with  either  of 
the  Eisemann  dash  coils,^type  DC  or  type  DCR,  Fig.  231.  The  coils 
differ  only  in  the  arrangement  for  starting  on  the  spark,  the  DC  having  a 
push-button  giving  a  single  spark,  provided  the  motor  happens  to  stand 
with  the  battery  breaker  open;  whereas  the  DCR  has  a  mechanical 
ratchet  device,  delivering  a  shower  of  sparks  regardless  of  the  crank 
position  of  the  engine. 

A  rapid  back  and  forth  motion  of  the  starting  handle  on  the  front 


MODERN  HIGH-TENSION  MAGNETOS 


183 


of  the  DCR  coil  causes  the  toothed  ratchet  in  the  center  to  oscillate  the 
lever  B,  Fig.  232,  which,  in  turn,  makes  contact  alternately  at  C  and  £>.. 
If  the  switch  is  on  battery  position  and  the  battery  breaker  points  in  the 
magneto  are  closed,  as  they  normally  are,  a  rapid  sequence  of  sparks  will 


Type  DCR  coil.  Type  DC  coil. 

FIG.  231.— Dash  coil  and  switch  units  for  Eisemann  high-tension  dual  magneto,  Type  GR4. 

occur  at  the  plugs.     This  shower  of  sparks  is  much  more  effective  for 
starting  on  compression  than  a  single  spark. 

A  circuit  diagram  of  the  system,  including  the  coil  connections  for  the 
different  switch  positions,  is  shown  in  Fig.  233.  As  may  be  seen,  the 
battery  breaker  operates  in  much 
the  same  manner  as  the  correspond- 
ing part  on  the  magneto.  It  is 
actuated,  mechanically,  by  two 
polished  steel  cams  attached  to  the 
magneto  breaker,  but  if  is  entirely 
separate,  electrically,  from  the 
latter.  Like  the  magneto  breaker, 
the  battery  breaker  causes  the  spark 
to  occur  at  the  instant  of  separation 
of  the  contact  points.  For  practi- 
cal reasons,  this  interruption  is 
timed  to  take  place  10°  later  than 
the  magneto,  but  is,  naturally, 
subject  to  the  same  degree  of  ad- 
vance and  retard,  being  mounted 
in  the  same  timing  lever  body. 
Both  breakers  are  protected  by  the  same  waterproof  cap  and  are  easily 
exposed  to  view. 

Both  sets  of  contact  points  should  be  adjusted  to  open  from  .010  in. 
to  .014  in.     The  distributor  is  the  same  as  the  G4  except  that  there  is  no 


FIG.  232.— Type  DCR  coil  with  front 
plate  removed  showing  mechanism  for  start- 
ing on  the  spark. 


184 


AUTOMOTIVE  IGNITION  SYSTEMS 


MODERN  HIGH-TENSION  MAGNETOS  185 

connection  between  the  lower  carbon  brush  and  the  center  one.  Cables 
lead  from  each  of  these  brushes  to  the  switch  portion  of  the  coil,  enabling 
the  center  brush  to  be  connected  to  the  lower  one  when  running  on  the 
magneto  or  to  the  coil  when  running  on  the  battery. 

If  for  any  reason  it  is  desired  to  operate  the  magneto  without  the 
coil  and  switch  unit,  it  may  be  operated  as  an  independent  high-tension 
magneto,  the  same  as  the  type  G4,  by  connecting  the  cables  marked  H 
and  HM  on  the  distributor  head,  making  a  direct  path  for  the  high-tension 
current  from  the  collector  ring  to  the  distributor. 

The  Eisemann  type  GS-4  magneto  is  very  similar  in  construction  to 
the  type  G4  with  the  exception  that  it  is  slightly  smaller  throughout. 

116.  Timing  of  the  Eisemann  Magneto  to  the  Engine  for  Variable 
Spark. — Since  the  spark  occurs  when  the  primary  circuit  is  broken  by 
the  opening  of  the  platinum  contacts  on  the  breaker  mechanism,  it  is 
necessary  that  the  magneto  be  timed  so  that  at  full  retard  position  of  the 
timing  lever  body,  the  platinum  contacts  just  begin  to  open  when  the 
respective  piston  of  the  engine  has  reached  its  highest  point  on  the  com- 
pression stroke.     The  engine  should  be  turned  by  hand  until  piston  of 
No.  1  cylinder  is  on  dead  center  (firing  point).     The  distributor  plate 
should  then  be  removed  from  the  magneto  and  the  driving  shaft  turned 
until  the  setting  mark  on  the  distributor  disc  is  in  line  with  the  setting 
screw  as  shown  in  Fig.  230.     (For  a  magneto  rotating  clockwise,  setting 
mark  R  is  used,  and  for  anti-clockwise,  setting  mark  L  is  used.)     With 
the  armature  in  this  position  and  the  timing  lever  body  fully  retarded, 
the  platinum  contacts  of  the  magneto  breaker  are  just  opening,  and  the 
metal  insert  of  the  distributor  disc  is  in  connection  with  the  carbon  brush  for 
No.  1  cylinder.     The  driving  medium  must  now  be  fixed  to  the  armature 
shaft  without  disturbing  the  position  of  the  latter,  and  the  cables  con- 
nected to  the  plugs  in  their  proper  order  of  firing. 

It  has  been  found  advisable  in  practice  to  time  the  battery  spark 
slightly  later  than  that  of  the  magneto  itself.  For  this  reason,  the 
battery  breaker  on  the  Eisemann  dual  type  magneto  is  permanently 
arranged  to  open  10°  later  than  the  magneto  breaker,  although  subject 
to  the  same  degree  of  advance  and  retard. 

117.  The  Eiseinann  Magneto  with  Automatic  Spark  Advance. — The 
Eisemann  automatic  spark  control  magneto  is  of  the  same  construction 
as  the  standard  high-tension  instrument  with  the  addition  of  the  auto- 
matic mechanism,  Fig.  234.     The  automatic  control  of  the  spark  is  accom- 
plished by  the  action  of  centrifugal  force  on  a  pair  of  weights  attached  at 
one  end  to  a  sleeve  through  which  runs  the  shaft  of  the  magneto,  and 
hinged  at  the  other  end  to  the  armature.     Two  helicoidal  splines,  which 
engage  with  similarly  shaped  splines  in  the  sleeve,  run  along  the  arma- 
ture shaft.     A  coiled  spring  pressing  against  the  inner  edge  of  the  sliding 
block  normally  keeps  the  governor  closed  when  the  engine  is  idle  or 


186 


AUTOMOTIVE  IGNITION  SYSTEMS 


barely  turning  over.  In  this  position  the  spark  is  fully  retarded.  Figure 
235  shows  the  armature  with  the  control  mechanism  mounted  in  place, 
removed  from  the  magneto.  In  this  illustration,  the  weights  are  shown 
in  the  position  of  full  spark  retard. 

As  the  engine  speeds  up,  the  centrifugal  force  acting  on  the  governor 
weights  causes  the  latter  to  spread  out,  drawing  along  the  shaft  the  sliding 


ANTJ-KNOCKiNG  WEIGH 
GOVERNOR  WEIGH 
BALL-BEARING 
PRING 


FIG.  234. — Eisemann  magneto  with  automatic  spark  advance. 

block,  through  which  runs  the  helically  cut  shaft,  keyed  to  the  armature, 
and,  consequently,  causing  the  latter  to  change  its  relative  position  to 
the  pole  pieces.  This  causes  an  earlier  opening  of  the  contact  breaker. 
The  spark  also  occurs  earlier,  or  is  " advanced".  Naturally,  the  higher 
the  engine  speed,  the  further  the  sliding  block  will  travel,  and  the  greater 


FIG.  235. — Eisemann  magneto  armature  showing  automatic  spark  advance  mechanism. 

will  be  the  amount  of  advance.  As  soon  as  the  speed  of  the  engine  de- 
creases, the  action  of  the  helical  sleeve  and  the  spring  gradually 
closes  the  governor  and  " retards"  the  spark. 

With  this  method  of  advance,  the  moment  of  current  induction  in 
the  high-tension  winding  is  brought  about  earlier  by  moving  the  entire 
armature,  and  with  it  the  contact  breaker  or  interrupter.  The  cams, 


MODERN  HIGH-TENSION  MAGNETOS  187 

which  lift  the  contact  lever  and  cause  the  breaker  in  the  primary  circuit 
to  open,  are  fixed  in  the  correct  position,  and  thus  the  break  occurs  only 
at  the  moment  when  the  current  in  the  winding  is  strongest. 

To  apply  the  automatic  control  to  any  engine  the  manufacturers 
have  produced  spindles  of  varying  pitches  to  give  19,  25,  38,  45,  and  60° 
of  spark  advance.  For  use  in  connection  with  these  spindles,  there  are 
sixteen  different  springs.  By  using  these  different  springs  in  connection 
with  the  governor  mechanism,  it  is  possible  to  prodvce  160  different 
advance  curves.  Many  more  curves  can  be  produced  by  varying  the 
length  of  the  stop  on  the  bronze  nut.  Many  engines  require  a  great  deal 
of  advance;  others  will  permit  of  only  a  few  degrees.  It  is  necessary  to 
take  into  consideration  the  size  and  shape  of  the  combustion  chamber, 
the  compression,  the  position  of  the  spark  plugs,  and  the  speed  of  the 
engine.  It  is  universally  acknowledged  that  an  engine  of  high  compres- 
sion will  give  a  quicker  burning  mixture  and  will  not  require  or  stand  so 
early  a  spark  as  one  of  lower  compression.  The  makers  of  this  magneto 
have  made  a  study  of  the  requirements  of  the  different  engines  on  the 
market  and  are  prepared  to  furnish  an  instrument  with  the  spark  advance 
mechanism  properly  adjusted  to  give  the  range  of  advance  needed  on 
the  particular  make  of  engine  for  which  it  is  ordered. 

118.  Eisemann  Impulse  Starter. — One  serious  objection  to  magneto 
ignition  is  the  complication  introduced  by  the  added  battery  or  dual 
equipment  which  furnishes  the  spark  when  starting  the  engine.  The 
ordinary  magneto  does  not  give  a  spark  of  sufficient  intensity  at  cranking 
speeds  to  fire  the  gas  in  the  cylinder.  This  drawback  has  been  overcome 
by  the  makers  of  the  Eisemann  magneto  by  installing  the  Eisemann 
impulse  starter  on  the  magneto  drive.  This  gives  a  hot  spark  even  when 
the  engine  is  cranked  slowly  by  hand  since  the  armature  is  snapped  past 
the  firing  point  by  a  strong  coiled  spring.  Figure  236  is  a  diagrammatic 
sketch  of  this  mechanism.  It  may  be  attached  to  any  model  of  the  Eise- 
mann magneto  and  has  no  effect  on  the  operation  of  the  magneto  at 
ordinary  running  speeds.  At  low  engine  speeds,  it  causes  the  armature 
of  the  magneto  to  rotate  in  a  series  of  jumps  instead  of  uniformly.  These 
jumps  cause  the  armature  to  cut  the  lines  of  force  from  the  magnets  at 
the  same  speed  as  when  the  engine  is  turning  over  rapidly,  so  that  a  hot 
spark  is  generated  in  either  case. 

The  starter  consists  of  a  driving  tube  A  and  a  driven  tube  or  cup  B, 
the  two  being  connected  by  a  spring.  Within  the  driven  cup  is  a  loose 
ring  C,  called  the  trigger,  this  ring  having  a  projection  which  extends 
through  a  slot  in  the  periphery  of  the  cup.  At  the  bottom  of  the  coupling 
is  a  notched  bar  so  placed  that  as  the  cup  revolves,  the  notch  registers 
with  the  slot  in  the  cup,  so  that  the  trigger  lip  drops  down  by  gravity, 
catches  in  the  notch,  and  locks  the  cup  against  rotation.  This  is  the 
condition  shown  in  view  C.  When  the  lip  has  engaged  the  notched  bar 


188 


AUTOMOTIVE  IGNITION  SYSTEMS 


and  the  cup  stops  revolving,  the  driving  tube  continues  to  turn.  This 
compresses  the  spring  against  a  driving  pin  on  the  tube  and  a 
block  fixed  to  the  cup.  At  the  proper  point  the  cam  on  the  trigger 
ring  engages  that  on  the  tube  and  lifts  the  trigger  out  of  the  notch  in 
the  bar;  the  compressed  spring  then  spins  the  armature  of  the  magneto 
past  the  firing  point  and  provides  a  hot  spark.  At  cranking  speeds  the 
trigger  is  caught  again  and  again  as  it  passes  the  notch;  but  when  the 
engine  fires,  the  speed  immediately  increases  to  the  point  where  the  trigger 
ring  is  kept  from  entering  the  notch  by  centrifugal  force.  At  this  speed 


DRIVEN 

CUP  -.. 


DRIVIN3 
MEMBER 


ARMATURE 
SHAFT 


Dff/VEN 
i'CUP 


FIG.  236. — Diagrammatic  sketch  of  Eisemann  impulse  starter. 

the  coupling  acts  as  a  solid  connection  between  the  drive  and  the  arma- 
ture. The  impulse  starter  removes  any  necessity  for  auxiliary  battery 
ignition  for  starting  on  heavy  duty  engines  since  a  hot  fat  spark  is 
generated  at  any  speed,  regardless  of  how  slowly  the  crank  is  turned. 
This  is  especially  desirable  on  heavy  truck  and  tractor  engines. 

119.  Simms  High-tension  Dual  Ignition  System. — The  Simms  dual 
ignition  system  is  a  combination  of  the  high-tension  type  of  magneto, 
Fig.  237,  in  which  the  high-tension  current  is  developed  in  a  high-tension 
winding  mounted  directly  on  the  armature,  and  an  added  battery  auxil- 


MODERN  HIGH-TENSION  MAGNETOS 


189 


iary  circuit  for  starting  purposes.  The  battery  current  is  broken  by  the 
regular  magneto  interrupter,  the  battery  circuit  being  introduced  to  the 
low-tension  armature  winding  at  this  point  as  shown  in  the  wiring  dia- 


FIG.  237. — Simm's  dual  high-tension  magneto,  type  SU6-S. 

gram,  Fig.  238.     The  contact  breaker  is  so  designed  that  its  action  is 
improved  by  the  centrifugal  force  developed  at  high  speeds.     This  dual 


FIG.  238. — Wiring  diagram,  Simm's  dual  magneto,  type  SU6-S. 

magneto  is  known  as  type  SU6-S.  The  dual  coil,  Fig.  239,  is  used  with 
this  equipment. 

A  special  feature  of  the  Simms  magneto  is  the  design  of  the  pole  pieces 


190 


AUTOMOTIVE  IGNITION  SYSTEMS 


which  have  extensions  on  the  edges  following  the  direction  of  rotation  of 
the  armature,  Fig.  240.  These  extensions  keep  the  edges  of  the  armature 
shuttle  within  the  influence  of  the  pole  in  all  positions  from  full  retarded 
spark  to  full  advanced  spark.  The  result  is  that  at  the  moment  of  break- 
ing the  circuit,  the  edge  of  the  shuttle  is  never  widely  separated  from  the 
edge  of  the  pole  piece,  thus  giving  a  spark  of  full  intensity  for  all  positions 
of  the  armature  within  the  limits  of  spark  advance. 

120.  The  Berling  High-tension  Dual  Magneto. — Berling  magnetos 
are  of  the  true  high-tension  rotating  armature  type.  The  independent 
type  magneto  is  complete  in  one  unit  and,  without  the  use  of  a  separate 
coil,  produces  a  hot  flame  spark  capable  of  rapidly  raising  the  temperature 
of  the  explosive  mixture  in  the  cylinder  to  the  flash  point.  The  cams 
which  operate  the  interrupter  are  integral  parts  of  the  interrupter  housing. 
The  interrupter  can  be  inspected  while  the  magneto  is  running  to  ascer- 


FIG.  239. — Simm's  dual  coil  and  switch.         FIG.  240. — Pole  pieces,  Simm's  magneto. 

tain  if  it  is  working  properly.  Figure  241  is  an  X-ray  view  of  the  inde- 
pendent Berling  magneto. 

The  Berling  dual  system  is  a  true  dual  system  consisting  of  two  in- 
dependent sources  of  ignition,  having  common  control  and  distribution. 
The  dual  feature  is  made  possible  by  adding  to  the  independent  type  of 
Berling  magneto  a  battery  timer  and  a  different  form  of  yoke  or  brush 
holder.  The  only  part  of  the  electric  circuit  of  the  magneto  that  is  used 
in  common  with  the  battery  system  is  the  distributor.  The  dual  system 
may  use  either  the  vibrating  or  the  non-vibrating  type  of  coil.  The  run- 
ning operation  of  both  types  is  the  same,  the  difference  being  in  the  char- 
acteristics of  the  starting  spark.  The  vibrating  coil  provides  a  more 
certain  starting  ignition  since  the  succession  of  sparks  serves  to  raise 
the  temperature  of  the  mixture  in  the  cylinder  to  the  firing  point. 

Figure  242  shows  the  Berling  dual  magneto.  This  magneto  is  similar 
to  the  independent  type  with  the  exception  of  a  dual  yoke  or  brush 


MODERN  HIGH-TENSION  MAGNETOS 


191 


holder  with  two  terminals  which  permit  the  high-tension  current  from 
the  coil  and  battery  to  be  connected  to  the  magneto  distributor,  and  a 
battery  timer  which  is  incorporated  in  the  cam  housing  which  encloses 


OIL  WELL  COVER 


DISTRIBUTOR  GEAR 
DISTRIBUTOR  FINGER 

DISTRIBUTOR   SLOCK 
HIGH  TENSION  TERMINAL  NUT 


PINION 


INTERRUPTER 


CAM    HOUSING   CLAMP 


CAM   HOUSING  COVER 


MAGNET  STRAP 
DRIVING  END  COVER 

RUSH   HOLDER  ASSEMBLY 

SAFETY  GAP 
DRIVING   END  BEARING 


CAM   HOUSING 


FIG.  241. — X-ray  view  of  Berling  high-tension  independent  magneto. 

the  magneto  interrupter.  The  common  timing  lever  thus  controls 
both  the^magneto  and  the  battery  spark.  Means  are  provided  for  ad- 
justing the  timing  of  the  two  sparks,  to  provide  the  best  relation  for 
proper  timing.  The  two  systems  are 
practically  independent  since  the  only 
part  used  in  common  is  the  magneto 
distributor.  The  failure  of  either  unit 
does  not  affect  the  other,  unless  a  com- 
plete mechanical  breakdown  occurs. 
The  Berling  dual  system  may  be  ar- 
ranged to  suit  any  desired  form  of  in- 
stallation. The  coil  and  switch  are 
supplied  as  a  single  unit,  or  separately. 
The  external  wiring  diagram  of  the 
Berling  dual  high-tension  magneto  is 
shown  in  Fig.  243.  This  figure  shows 
the  two  high-tension  connections  at 
the  drive  end  of  the  magneto.  One 
of  these  connections  carries  the  high- 
tension  current  generated  in  the  dual  coil;  the  other  carries  the  magneto 
secondary  current.  The  switch  disconnects  the  magneto  secondary  cir- 
cuit from  the  distributor,  when  the  battery  ignition  is  being  used,  thus 


FIG.    242. — Berling    high-tension    dual 
magneto,  type  ED-61. 


192 


AUTOMOTIVE  IGNITION  SYSTEMS 


preventing  the  battery  high-tension  current  from  reaching  ground  through 
the  secondary  winding  on  the  magneto. 

121.  The  Kingston  Model  O  High-tension  Magneto. — The  Kingston 
model  0  high-tension  magneto,  Fig.  244,  has  but  one  winding  on  the 


FIG.  243. — External  wiring  diagram  of   Berling  high-tension  dual  magneto,  type  SU-61. 

rotating  armature.  The  primary  current  is  generated  in  the  armature 
and  broken  at  the  contact  points  in  the  interrupter.  The  high-tension 
current  is  produced  in  the  secondary  winding  of  the  induction  coil  that  is 

placed  under  the  arch  of  the  mag- 
nets in  the  upper  part  of  the  instru- 
ment. Figure  245  is  a  sectional 
view  of  this  instrument  showing  all 
the  parts.  The  armature  and  the 
primary  current  generating  coil 
carried  on  it  are  shown  in  the  lower 
part  of  the  figure.  At  the  left  end 
of  the  armature  shaft  is  the  in- 
terrupter and  immediately  above 
it  the  distributor.  The  condenser 
is  directly  above  the  armature,  and 
under  the  arch  of  the  magnets  is 


FIG.  244. — Kingston  high-tension  magneto, 
model  O,  showing  impulse  starter  at  right. 


the  induction  coil  with  its  primary 
and  secondary  windings.  This 
magneto  is  complete  in  itself,  the  only  external  wiring  necessary  being 
the  leads  to  the  spark  plugs  and  another  lead  to  the  switch  for  grounding 
the  current  generated  in  the  armature  winding.  This  switch  is  used  for 
stopping  the  engine. 


MODERN  HIGH-TENSION  MAGNETOS 


193 


The  Kingston  magneto  was  developed  for  heavy  duty  engines  such  as 
those  used  in  trucks  and  tractors.  The  large  size  of  these  engines  pre- 
vents their  being  cranked  at  anything  but  the  slowest  speeds.  In  order 


852 


969A' 

683/ 
974o*975 


'360'  , 

X653'7 

651 


X533 


X537 


FIG.  245. — Sectional  view  of  Kingston  model  O  high-tension  magneto. 


INTERIOR  VIEW 
OF  BODY 


SECTION  THRU 
IMPULSE  STARTER 


INTER  for?  VIEW 
OF  DRIVER 


FIG.  246. — Kingston  impulse  starter. 

to  insure  a  good  spark  at  the  low  cranking  speeds,  the  impulse  starting 
mechanism,  shown  at  the  right  end  of  the  armature  shaft  in  Fig.  244 
and  disassembled  in  Fig.  246,  is  installed  in  the  magneto  drive.  The 


194 


AUTOMOTIVE  IGNITION  SYSTEMS 


impulse  starter  consists  of  a  driving  and  a  driven  member  with  a  coiled 
spring  between  them.  At  low  speeds,  a  third  ring-shaped  member  drops 
at  each  revolution  and  a  projection  on  the  ring  engages  a  projection  on  the 
body  of  the  magneto,  thus  preventing  the  further  rotation  of  the  arma- 
ture shaft.  The  driving  member  continues  to  rotate  and  winds  up  the 
coiled  spring.  At  a  certain  point,  the  projection  on  the  ring  member 


Advanced  spark.  Retarded  spark. 

FIG.  247. — Horseshoe-type    magnetos — relative   positions    of    armature    and   magnets   at 

the  moment  of  sparking. 

slips  off  of  the  stop  on  the  magneto  body.  This  releases  the  coiled  spring 
and  it  immediately  unwinds,  driving  the  armature  forward  with  a  quick 
jerk  past  the  firing  point  and  giving  a  hot  spark  for  starting.  At  ordinary 
engine  speeds,  the  ring  member  is  kept  from  dropping  and  engaging  the 
stop  by  centrifugal  force.  Under  this  condition,  the  magneto  is  driven 
constantly  at  engine  speed. 


Advanced  spark.  Retarded  spark. 

FIG.  248. — Mea  magneto — relative  position  of  armature  and  magneto  at  the  moment 

of  sparking. 

122.  The  Mea  Magneto. — The  Mea  magneto,  which  departs  in 
several  particulars  from  the  usual  magneto  construction,  is  designed 
to  give  a  wide  range  of  ignition  without  affecting  the  value  of  the  spark- 
ing current.  In  the  ordinary  horseshoe  type  of  magneto  with  fixed 
magnets,  any  change  in  the  time  of  the  spark  means  that  the  spark 


MODERN  HIGH-TENSION  MAGNETOS 


195 


is  produced  at  a  different  position  of  the  armature  with  respect  to  the 
magnets  as  shown  in  Fig.  247.  This  naturally  limits  the  spark  range 
to  that  part  of  the  current  wave  in  which  suitable  ignition  can  be  ob- 
tained. The  Mea  magneto  shifts  the  magnets  with  the  interrupter, 


FIG.  249. — Bell-shaped    magnet    of    Mea 
magneto. 


FIG.  250. — The  Mea  magneto. 


as  shown-  in  Fig.  248,  so  that  the  armature  is  always  in  the  same  rela- 
tion to  the  magnets,  regardless  of  the  .advance  or  retard  of  the  spark 
timing  lever.  With  the  standard  types  of  Mea  magnetos  the  spark- 
ing range  is  from  45°  to  70°.  If  necessary  this  range  can  be  increased. 


21    4     3    16   30    10 


FIG.  251. — Section  of  Mea  type  BH4  magneto. 

Although  the  Mea  magneto  is  also  offered  with  dual  equipment  for 
battery  starting,  the  makers  claim  that  the  battery  starting  is  not 
needed  because  of  the  fact  that  the  magneto  always  takes  full  advan- 
tage of  the  armature  current. 


196  AUTOMOTIVE  IGNITION  SYSTEMS 

The  magnets  are  bell-shaped,  as  shown  in  Fig.249,  and  are  so  placed 
that  their  axes  coincide  with  that  of  the  armature.  The  exterior  is 
seen  in  Fig.  250,  the  magnets,  distributor,  and  interrupter  housing 
being  cradled  in  the  frame  of  the  base  of  the  magneto.  The  timing 
lever  is  shown  at  the  right,  attached  directly  to  the  magnets.  Figure 
251  shows  the  internal  arrangement.  The  armature  is  of  quite  con- 
ventional design  with  the  driving  connection  at  32,  the  condenser  at 
21,  the  high-tension  collector  at  4,  and  the  interrupter  at  the  extreme 
right.  The  interrupter  is  built  on  a  disc,  13,  which  carries  the  platinum 
contacts  at  12,  the  movable  contact  being  adjustable  and  supported 
by  a  spring,  14.  This  spring  is  in  turn  fastened  to  the  insulated  plate, 
15,  which  receives  the  armature  current  through  the  screw,  16.  The 
interrupter  is  actuated  by  the  fiber  roller,  17,  which  is  also  carried  by 
the  disc,  13.  This  roller  is  actuated  by  a  cam  disc,  18,  which  is  provid- 
ed with  two  projections  and  is  attached  to  the  field  structure.  In 
this  way  the  spark  is  secured  at  certain  definite  relative  positions  of 
the  armature  and  magnets. 


CHAPTER  VIII 
MODERN   HIGH-TENSION  MAGNETOS— INDUCTOR  TYPES 

123.  Principles  of  the  Inductor  Type  Magneto. — Two  low-tension 
magnetos  of  the  inductor  type,  the  Remy  type  RL  and  the.  Ford,  have 
been  considered  in  Chapter  VI.  In  these  two  magnetos  the  cur- 
rent is  generated  in  coils  which  do  not  revolve  but  are  stationary.  In 
the  Ford  magneto,  the  coils  are  mounted  on  a  supporting  plate  while 
the  magnets  are  mounted  on  the  flywheel  and  revolve  past  the  station- 
ary coils.  As  the  magnets  pass  these  coils,  the  magnetic  lines  of  force 
from  the  magnets  cut  the  windings  of  these  coils  and  generate  a  cur- 
rent in  them.  In  this  instance,  the  coils  are  stationary  and  the  magnets 
revolve,  in  contrast  to  the  usual  magneto  that  has  been  described  up  to  this 
time.  In  the  Remy  type  RL  low-tension  magneto,  both  the  coil 
and  the  magnets  are  stationary,  the  magnetic  lines  of  force  being  made 
to  cut  the  windings  of  the  coil  by  the  movement  of  a  rotating  element 
consisting  of  two  heavy  wings  of  iron,  and  known  as  the  rotor  or  induct- 
or. The  movement  of  these  two  heavy  wings  of  iron  between  the  coil 
and  the  magnets  reverses  the  direction  of  the  lines  of  force  through  the 
coil.  At  the  moment  of  reversal  a  strong  current  is  induced  in  the 
coil;  consequently,  this  type  of  magneto  is  known  as  an  inductor  mag- 
neto and  all  magnetos  of  this  class,  that  is,  with  stationary  windings, 
.are  said  to  be  of  the  inductor  type. 

The  essential  difference  between  the  inductor  type  magneto  and 
the  rotating  armature  type  magneto  is  that  in  the  rotating  armature 
type  the  magnetic  lines  of  forces  are  nearly  stationary  and  the  arma- 
ture rotates,  causing  the  windings  on  the  armature  to  cut  the  station- 
ary (or  nearly  stationary)  lines  of  force.  In  the  inductor  type 
magneto,  on  the  other  hand,  the  coil  or  winding  is  stationary,  while 
the  magnetic  lines  of  force  are  made  to  change  their  position  with  re- 
spect to  the  coil  by  the  rotating  inductor,  thus  causing  the  moving 
lines  of  force  to  cut  the  stationary  winding  or  coil.  The  stationary 
winding  on  the  inductor  type  magneto  has  certain  advantages,  among 
which  may  be  mentioned  the  absence  of  numerous  sliding  electrical 
contacts. 

Figure  252  illustrates  the  methods  employed  in  generating  current 
in  the  two  types  of  magnetos.  The  revolving  armature  type  magneto 
is  represented  by  the  drawing  on  the  left.  The  magnet  is  stationary, 
the  coil  or  wire  being  moved  up  and  down  between  the  poles.  This 

197 


198 


AUTOMOTIVE  IGNITION  SYSTEMS 


motion  causes  the  wire  to  cut  the  lines  of  force  of  the  magnet  and  sets 
up  currents  that  flow  back  and  forth  in  the  wire  as  the  wire  is  moved 
up  and  down.  These  currents  are  shown  by  the  vibration  of  the  hand 
on  the  current  indicator.  The  right-hand  drawing  shows  the  action 


DIRECTION   OF 
MOTION    OF   MAGNET 


DIRECTION    OF 
'MOTION     OF      WIRE 


CURRENT 
IN   WIRE 


STATIONARY 
MAGNET 


Armature  type. 


Inductor  type. 


FIG.  252. — Comparison  of  the  methods  of  generating  current  in  revolving  armature  and  in 

inductor  types  of  magnetos. 

in  an  inductor  type  magneto.  The  wire  loop  is  placed  on  the  edge 
of  the  shelf  and  the  poles  of  the  magnet  are  moved  up  and  down  past 
the  wire.  This  motion  of  the  magnet  causes  the  lines  of  force  to  cut 


Model  T.  Model  TK. 

FIG.  253.— K-W  inductor  type  magnetos  for  high  speed  automobile  engines. 

the  wire  loop  and  sets  up  currents  that  flow  back  and  forth  in  the  loop 
as  in  the  previous  case. 

124.  The    K-W   High-tension    Magneto.— The    K-W   high-tension 
magneto  is  made  in  two  models,  the  model  T  illustrated  in  Fig.  253, 


MODERN  HIGH-TENSION  MAGNETOS 


199 


suitable  for  high-speed  engines  with  small  cylinders,  and  the  Model 
H  illustrated  in  Fig.  254  suitable  for  large  slow-speed  heavy  duty 
engines.  Both  models  may  be  fitted  with  the  K-W  impulse  starter 
for  easy  starting  of  engines  that  are  so  large  that  hand  cranking  is  im- 


Model  H.  Model  HK. 

FIG.  254.- — K-W  inductor  type  magnetos  for  low  speed,  heavy  duty  engines. 

possible  at  any  but  the  slowest  speeds.  The  K-W  magneto,  being 
of  the  true  high-tension  type,  is  complete  in  itself,  requiring  no  external 
coils  or  other  apparatus. 


mmm 


FIG.  255. — Interior  view  of  K-W  magneto  showing  rotor  and  coil. 

Figure  255  shows  the  simple  internal  construction  of  the  K-W  mag- 
neto. Instead  of  having  wires  wound  longitudinally  around  a  revolving 
armature,  it  has  a  stationary  flat  winding  of  the  " pancake"  type  as  is 
shown  in  the  center  of  Fig.  256.  The  rotor  changes  the  direction  of 


200 


AUTOMOTIVE  IGNITION  SYSTEMS 


magnetic  flux  through  the  winding  four  times  per  revolution.  It  re- 
volves on  two  sets  of  annular  ball  bearings  and  does  not  rub  against  or 
touch  any  part  of  the  magneto.  The  breaker  or  interrupter  is  mounted 
on  one  end  of  the  rotor  shaft. 


FIG.  256.— K-W  rotor  and  coil. 


FIG.  257. — Magnetic  circuit  in  the  K-W  magneto. 

The  principle  on  which  the  K-W  high-tension  magneto  operates  is 
shown  in  Fig.  257.  This  is  a  perspective  view  of  the  stationary  coil, 
the  pole  pieces,  and  the  rotor.  The  rotor  is  made  up  of  two  rectangu- 
lar blocks  of  soft  iron.  These  blocks  are  not  made  of  one  solid  piece, 
but  are  built  up  of  thin  sheet  iron  stampings.  This  laminated  construe- 


MODERN  HIGH-TENSION  MAGNETOS  201 

tion  has  been  found  best  for  all  parts  of  electrical  apparatus  that  are 
subjected  to  the  rapid  reversal  of  magnetic  lines  of  force  since  it  reduces 
certain  losses  present  in  the  solid  construction.  The  two  rotor  blocks  are 
placed  at  right  angles  to  each  other  some  distance  apart  on  the  rotor 
shaft.  The  space  between  the  blocks  is  occupied  by  the  coil  which  is 
supported  in  this  position  and  remains  stationary,  while  the  rotor  shaft 
turns  within  it  and  the  rotor  blocks  rotate  on  either  side.  The  pole 
pieces  do  not  extend  completely  around  the  moving  parts,  as  in  the  rotat- 
ing armature  type  of  magneto,  but  extend  only  over  the  upper  portion 
of  this  space.  The  drawing  to  the  left  in  the  figure  shows  one  end.  of  the 
rotor  block  on  the  far  side  of  the  coil  in  contact  with  the  N  pole  piece 
and  one  end  of  the  near  rotor  block  in  contact  with  the  S  pole  piece.  In 
this  position  of  the  rotor  the  magnetic  path  from  one  pole  to  the  other  is 
as  follows:  The  magnetic  lines  leave  the  N  pole  and  pass  through  the 
far  rotor  block  until  they  come  to  the  rotor  shaft,  then  pass  through  the 
rotor  shaft  and  through  the  center  of  the  coil  to  the  other  rotor  block 
from  which  they  enter  the  S  pole  of  the  magnets.  The  drawing  to  the 
right  in  the  figure  shows  conditions  one-quarter  of  a  revolution  of  the  rotor 
later.  The  near  rotor  block  is  now  in  contact  with  the  N  pole  while  the 
far  block  is  in  contact  with  the  S  pole.  The  path  of  the  magnetic  lines 
of  force  is  now  from  the  N  pole  into  the  near  rotor  block,  through  the 
rotor  shaft  and  the  center  of  the  coil  to  the  far  rotor  block  and  into  the  S 
pole.  The  arrows  in  the  two  drawings  show  the  magnetic  path  in 
each  case.  It  will  be  noticed  that  the  direction  of  the  magnetic  flux 
through  the  center  of  the  coil  is  opposite  in  direction  in  the  second  case 
to  what  it  was  in  the  first  case.  The  reversal  takes  place  every  time  the 
rotor  is  turned  one-quarter  of  a  revolution.  This  reversal  of  the  magnetic 
flux  through  the  coil  every  quarter  revolution  gives  four  current  pulses 
every  revolution.  The  rotating  armature  type  magneto  gives  only  two 
pulses  of  current  per  revolution.  The  K-W  magneto,  therefore,  is 
capable  of  furnishing  ignition  for  any  engine  at  but  one-half  the  custom- 
ary magneto  speed.  The  ability  to  furnish  four  sparks  per  revolution 
is  of  great  advantage  in  eight-  and  twelve-cylinder  engines.  The  mag- 
neto shaft  in  an  eight-cylinder  engine,  using  a  magneto  of  this  type, 
rotates  at  crankshaft  speed,  while  that  for  a  twelve-cylinder  rotates  at 
one  and  one-half  times  crankshaft  speed.  Other  types  of  magnetos 
producing  two  sparks  per  revolution  of  the  armature  require  a  magneto 
speed  of  twice  crankshaft  speed  for  the  eight-cylinder  engine  and  three 
times  crankshaft  speed  for  the  twelve-cylincler  engine. 

Figure  258  shows  the  current  wave  generated  by  the  shuttle  type 
magneto,  and  Fig.  259  shows  the  current  wave  produced  by  the  K-W 
magneto.  The  K-W  construction  gives  twice  the  number  of  current 
impulses  per  revolution. 

A  cross  section  of  the  K-W  model  T  high-tension  magneto  is  shown 


202 


AUTOMOTIVE  IGNITION  SYSTEMS 


in  Fig.  26(X  This  shows  the  winding  between  the  two  rotor  blocks  in  the 
lower  part  of  the  magneto.  This  winding  consists  of  two  parts,  the  pri- 
mary and  the  secondary.  The  breaking  of  the  primary  circuit  builds 


FIG.  258. — Current  waves  of  the  rotating 
armature  type  magneto. 


FIG. 


259. — Current  waves  of  the  K-W 
ductor  type  magneto. 


up   in   the   secondary  circuit   the   high-tension  surge  of  current  which 
is  distributed  to  the  proper  spark  plug  by  the  distributor  at  the  upper 


2.  Gear  housing. 

3.  End  piece. 

4.  Magneto  case. 

5.  Triangular  end  piece. 
8.  Distributor  gear. 

16.  Pinion. 

21.  Distributor  block. 

26.  Distributor  gear  moulding. 

33.  Circuit  breaker  cap. 

35.  Terminal  thumb  nut. 

41.  Magneto  cover. 

46.  'Condenser  case. 

50.  Distributor  block  window. 

54.  Dust  washer  cap. 

62.  Distributor  shaft  washer. 

67.  Cam. 

70.  Cam  retainer  nut. 

71.  Magnet. 

73.   Rotor  shaft  bearing. 


74.  Rotor  shaft  bearing. 

97.  Distributor  gear  shaft. 

102.  Distributor  brush. 

108.  Distributor  shaft  retainer  spring. 

110.  Distributor  block  screw. 

118.  End  piece  screw. 

141.  Primary  circuit  plunger. 

142.  Primary  plunger  thumb  nut. 

144.  Condenser  case  screw. 

145.  Condenser  case  screw  nut. 
182.  Dust  washer. 

184.  Magneto  base. 

185.  Rotor  shaft. 
187.  Windings. 
192.  Cover  plate. 

195.  Condenser. 

196.  Gear  housing  oil  cover. 

197.  End  piece  oil  cover. 

198.  High-tension  lead. 


FIG.  260. — Cross  section  of  K-W  high-tension  magneto,  model  T. 

right  part  of  the  figure.  The  condenser  is  located  under  the  arch  of  the 
magnets  as  shown  at  195. 

The  impulse  starter  used  on  the  K-W  magneto  is  similar  to  the  ones 


MODERN  HIGH-TENSION  MAGNETOS 


203 


already  described.  However,  instead  of  being  automatic  in  its  operation, 
thus  coming  into  action  every  time  the  speed  of  the  engine  drops  below 
a  certain  point,  it  is  normally  rendered  inactive  by  a  latch  or  catch. 
This  catch  must  be  tripped  before  cranking  the  engine,  thus  allowing 
the  impulse  starter  to  come  into  play  and  snap  the  rotor  rapidly  past 
the  firing  point,  giving  a  hot  spark  for  starting.  As  soon  as  the  engine 
fires  and  comes  up  to  speed,  the  catch  automatically  hooks  up  and  again 
renders  the  impulse  starter  inactive.  K-W  magnetos  fitted  with  the 
impulse  starter  are  designated  by  the  letter  K  following  the  regular 
model  letter.  For  instance,  a  model  T  magneto  fitted  with  an  impulse 
starter  is  known  as  a  model  TK.  The  impulse  starter  is  shown  in  place 
on  the  model  TK  in  Fig.  253  and  on  the  model  HK  in  Fig.  254. 


FIG.  261. — K-W  model  T  magneto  with  breaker  housing  removed. 

The  K-W  model  T  high-tension  magneto  is  shown  in  Fig.  261  with  the 
breaker  housing  removed  for  the  purpose  of  showing  the  construction  of 
the  interrupter.  The  breaker  points,  C,  are  carried  on  the  breaker  housing 
and  may  be  examined  and  adjusted  with  the  magneto  running.  The 
breaker  housing  fits  into  the  cup  or  recess  B  and  is  held  in  place  by  the 
retaining  spring  marked  T-53  which  fits  over  the  stud  AA  and  is  held  on 
by  the  insulating  washers,  hexagonal  nuts,  and  thumb  nut  shown  at  A. 
These  washers,  nuts,  etc.  are  shown  correctly  assembled  on  the  stud  at 
D.  In  assembling  the  breaker  housing  parts,  care  should  be  taken  that 
these  washers  are  put  on  exactly  as  shown.  The  dust  should  be  cleaned 
off  of  the  breaker  housing  and  other  parts  of  the  magneto  at  frequent 


204 


AUTOMOTIVE  IGNITION  SYSTEMS 


intervals.     Any  rough  edges  on  the  contact  points  should  be  smoothed  off 
with  a  fine  file  or  oil  stone. 


SWITCH 


r 


PRIMARY 
BREAKER    POINT5    ' 


PARK    GAP 


CONDENSER- 


FIG.  262. — Circuit  diagram,  K-W  model  T  high-tension  magneto. 

Figure  262  is  the  circuit  diagram  for  the  K-W  model  T  high-tension 
magneto.     The  primary  and  secondary  windings  are  contained  in  the 

stationary  coil.  The  ignition  switch  serves  to 
ground  the  primary  current  when  the  engine 
is  to  be  stopped.  The  high-tension  winding 
is  protected  by  a  spark  gap.  A  condenser  is 
connected  in  parallel  with  the  breaker  points 
for  the  purpose  of  preventing  excessive  spark- 
ing at  the  points  and  to  absorb  the  arcing, 
or  hang-over  current,  thus  causing  a  rapid  col- 
lapse of  the  primary  field  and  producing  a 
more  vigorous  spark  in  the  secondary  circuit. 
The  K-W  model  W  magneto,  Fig.  263,  is 
a  high-speed  instrument  especially  designed 
for  airplane  engines  of  eight  or  twelve  cylin- 

FIG.    263.— K-W    model   W  ders.     The    distributor    block    is  of  liberal 
magneto   for   an    eight-cylinder  dimensions,  permitting  the  distributor  seg- 

engme.  & 

ments  to  be  spaced  sufficiently  far  apart  to 

eliminate   any   possibility   of  arcing   between    segments.     The    circuit 
breaker  parts  are  of  ample  size  to  withstand  the  rapid  movements  and 


FIG.  264. — K-W  magneto  interrupter  cams. 

vibrations  of  the  high-speed  magneto.     The  possibility  of  ignition  failure, 
due  to  the  loosening  of  screws,  is  prevented  by  using  rivets  to  hold  the 


MODERN  HIGH-TENSION  MAGNETOS  205 

important  parts  together.  The  construction  throughout  is  very  rugged. 
For  engines  which  are  hard  to  pull  over  compression  in  starting,  the  reg- 
ular K-W  impulse  starter  may  be  fitted. 

The  interrupter  cams  used  with  the  K-W  magneto  are  shown  in 
Fig.  264.  These  are  made  to  give  a  single  spark,  two  sparks,  or  four 
sparks  per  revolution  of  the  rotor  shaft.  The  speed  of  the  rotor  varies 
with  the  number  of  cylinders  on  the  engine.  A  single-cylinder  four-stroke 
engine  magneto  uses  cam  No.  1  and  is  driven  at  crankshaft  speed.  This 
gives  a  spark  at  the  end  of  the  exhaust  stroke  as  well  as  at  the  regular 
firing  time.  The  two-cylinder  engine  magneto  uses  cam  No.  1  at  crank- 
shaft speed,  giving  one  spark  per  revolution  of  the  crankshaft.  The 
three-cylinder  engine  uses  cam  No.  1  driven  at  1J^  times  crankshaft 
speed.  The  four-cylinder  engine  uses  cam  No.  2  at  crankshaft  speed, 
giving  two  sparks  per  revolution  of  the  crankshaft.  The  six-cylinder 
engine  uses  cam  No.  2  at  1J^  times  crank- 
shaft speed,  giving  three  sparks  per  rev- 
olution of  the  crankshaft.  The  eight- 
cylinder  engine  uses  cam  No.  3  driven  at 
crankshaft  speed,  giving  four  sparks  per 
revolution  of  the  crankshaft.  The  twelve- 
cylinder  engine  uses  cam  No.  3  driven  at 
lJ/£  times  crankshaft  speed,  giving  six 
sparks  per  revolution  of  the  crankshaft. 
The  large  number  of  current  impulses  per 
revolution  of  the  rotor  allows  the  K-W 
magneto  to  be  driven  at  a  relatively  low 
speed — a  decided  advantage  in  high-speed 
multi-cylinder  ignition. 

125.  The  Dixie  Magneto  for  Four-  and 
Six-cylinder  Engines. — The  Dixie  high-tension  magneto,  the  four-cylinder 
model  of  which  is  shown  in  Fig.  265,  is  a  typical  inductor  type  instru- 
ment operating  on  what  is  known  as  the  "  Mason  Principle,"  with  a 
stationary  winding  and  a  rotating  inductor  or  rotor.  The  construction 
and  general  arrangement  of  the  various  parts  are  shown  in  Fig.  266, 
which  is  a  front  view  with  the  distributor  block  and  the  breaker  cover 
removed;  and  in  Fig.  267,  which  is  a  side  view,  with  the  cover  and  one  mag- 
net removed.  The  magnets  and  rotating  element  are  shown  in  Fig.  268 

It  will  be  noted  that  the  magneto  consists  principally  of  a  pair  of  mag- 
nets, a  rotor,  a  field  structure,  a  winding,  an  interrupter,  and  a  condenser 
The  rotor,  Fig.  269,  consists  'of  two  revolving  wings,  N  and  S,  separated 
by  a  bronze  center-piece,  B.  The  ends  of  the  wings  are  brought  intc 
contact  with  the  poles  of  the  magnets,  as  shown  in  Fig.  268,  and,  there- 
fore, bear  the  same  polarity  of  magnetism  as  the  poles  of  the  magnets 
with  which  they  are  in  contact.  This  polarity  of  the  wings  is  always  the 


206 


AUTOMOTIVE  IGNITION  SYSTEMS 


same  as  there  is  no  reversal  of  magnetism  through  them.  The  rotor  is 
surrounded  by  a  field  structure  which  carries  laminated  pole  extensions, 
on  which  the  winding  with  its  laminated  core  is  mounted.  As  the  rotor 
revolves,  the  magnetic  flux  penetrates  the  core  of  the  winding,  first  in 
one  direction  and  then  in  the  other,  according  to  the  position  of  the 
rotor  in  relation  to  the  poles  of  the  field  structure  as  shown  in  Figs.  270, 
271,  272,  and  273.  Figure  271  shows  the  rotor  in  such  a  position  that  the 
flux  enters  wing  N,  passes  through  the  core  C,  and  returns  to  wing  S  of 
the  rotor.  Figure  273  shows  the  flux  passing  through  the  coil  in  the 
reverse  direction. 


17 


16 


1.  Distributor  gear. 

2.  Distributor  disc. 

3.  Finger  spring  for  breaker  bar. 

4.  Cam  screw. 

5.  Breaker  bar  with  platinum  point. 

6.  Contact     screw      bracket      with 

bushings. 

7.  Platinum  contact  screw. 

8.  Breaker  cover. 


insulating 


9.   Ground  spring. 

10.  Thumb  nut  for  ground  stud. 

11.  Lock  washer  for  ground  stud  nut. 

12.  Washer  for  ground  stud. 

13.  Cam. 

14.  Distributor  block. 

15.  Thumb  nut  for  distributor  block. 

16.  Breaker  base. 

17.  Breaker  bar  spring. 


FIG.  266. — Front  view  of  Dixie  magneto  with  distributor  head  and  breaker  cover  removed. 

The  greatest  intensity  in  the  primary  circuit  occurs  when  the  rate  of 
change  of  flux  or  magnetic  lines  of  force  through  the  core  is  a  maximum. 
This  occurs  when  the  rotor  is  in  the  position  shown  in  Fig.  272,  where  the 
rotor  wings  have  just  reversed  the  direction  of  flux  through  the  core,  the 
gap  between  the  trailing  wing  corner  and  the  pole  piece  being  from  .015  in. 
to  .035  in.,  preferably  .020  in.  Consequently,  the  interrupter  contact 
points  should  be  adjusted  to  break  the  primary  circuit  when  the  rotor 
is  in  this  position.  A  circuit  diagram  of  the  magneto  is  shown  in  Fig.  274 
from  which  it  will  be  seen  that  the  primary  circuit  is  of  the  interrupted 


MODERN  HIGH-TENSION  MAGNETOS 


207 


primary  current  type.  The  breaking  of  the  primary  circuit  induces  a 
high-voltage  current  in  the  secondary  winding,  this  current  being  directed 
to  the  proper  spark  plug  by  a  distributor  driven  by  a  gear  on  the  rotor 
shaft.  The  condenser,  one  terminal  of  which  is  connected  to  the  insulated 
end  of  the  primary  coil  and  the  other  terminal  grounded  to  the  magneto 
frame,  is  mounted  on  the  top  of  the  coil. 


567 


1t 


1.  Condenser. 

2.  Magnet. 

3.  Gap  protector. 

4.  Oil  hole  cover,  front. 

5.  Stud  for  distributor  block. 

6.  Clamp  for  distributor  block. 

7.  Thumb  nut  for  distiibutor  block. 

8.  Hexagonal  nut  for  grounding  stud. 

9.  Thumb  nut  for  grounding  stud. 

10.  Grounding  stud. 

11.  Screw  and  washer  for  fastening  breaker. 

12.  Screw  and  washer  for  fastening  condenser  and 

primary  lead  to  winding. 

13.  Screw  and  washer  for  fastening  primary  lead 

tube  clamp. 


14.  Primary  lead  tube. 

15.  Primary  lead  tube  clamp. 

16.  Screw  and  washer  for  fastening  grounded  clip 

to  pole  structure. 

17.  .Rotor  shaft. 

18.  Drive  key. 

19.  Back  plate. 

20.  Oil  hole  cover,  back. 

21.  Grounding  clip. 

22.  Screw  and  washer  for  fastening  grounding  clip 

to  winding. 

23.  Winding. 

24.  Screw  and  washer  for  fastening  winding  to 

pole  structure. 


FIG.  267. — Side  view  of  Dixie  magneto  with  cover  and  one  magnet  removed. 


One  of  the  outstanding  features  of  the  Dixie  magneto  is  the  shifting 
of  the  pole  pieces  with  the  timing  lever,  upon  advancing  and  retarding 
the  spark.  This  permits  the  breaker  to  interrupt  the  primary  circuit  at 
all  times,  when  the  primary  current  is  flowing  at  its  maximum,  thus  caus- 
ing a  spark  of  maximum  intensity  at  all  positions  of  the  breaker. 

Since  the  coil  windings  are  not  on  a  revolving  armature,  the  interrupter 


208 


AUTOMOTIVE  IGNITION  SYSTEMS 


is  built  like  that  for  a  low-tension  magneto;  that  is,  the  interrupter 

mechanism  is  mounted  on  the  in- 
terrupter housing  and  the  cam  is  re- 
solved with  the  rotor  shaft.  This 
construction  permits  the  adjusting  of 
the  contact  points  with  the  engine 
and  magneto  running.  The  contacts 


FIG.  268. — Rotor  and  magnets  for  Dixie 
magneto. 


FIG.  269. — Rotating  element  in  Dixie 
magneto. 


270 


271 


272 


273 


FIG.  270  to  273. — Showing  the  principle  of  the  Dixie  magneto. 
MAGNETS 


POSITION  OF 
ROTOR  WING 
WHEN  BPEAKEP 
CONTACTS  OPEN 


ROTOR 


DISTRIBUTOR 
BLOCK 

BRASS  HIGH- 
TENSION  SEGMENT 
ON  COIL 


DISTRIBUTOR 
SEGMENT 


TIMEP  LEVER 


BREAKER  BASEL 


(SHOULD  OPEN  -OZOJj 


MAGNETO  GROUNDING 
CAM    TERMINAL  (INSULATED) 


GROUND  ^!EF 

MAGNETO    GROUNDING 
SWITCH 


GR. 


FIG.  274. — Circuit  diagram  of  Dixie  high-tension  magneto,  model  46. 

are  made  of  platinum  and  should  be  adjusted  to  open  .020  in.     This 


MODERN  HIGH-TENSION  MAGNETOS 


209 


adjustment  can  be  made  with  a  screwdriver,  as  shown  in  Fig.  275,  by 
turning  the  stationary  contact  screw  after  loosening  the  clamp  screw 
which  holds  it  firmly  in  place.  Care  must  be  exercised  to  retighten  the 
clamp  screw  after  adjusting. 

Magneto  Switch. — Extending  through  the  magneto  breaker  cover  is 
an  insulated  terminal  which  is  connected  to  the  insulated  end  of  the 
magneto  primary  winding.  This  terminal  is  also  connected  to  a  ground- 
ing switch  by  which  the  primary  winding  can  be  grounded  or  short 


FIG.    275. — Adjusting  contact  joints,  Dixie  magneto  odel  46. 


FIG.  276. — Dixie  magneto  switch.         FIG.  277. — Aero  four-cylinder  magneto. 

circuited,  and  ignition  prevented.  The  Dixie  magneto  switch  is  shown 
in  Fig.  276.  The  wire  leading  from  the  magneto  is  attached  to  one  of  the 
terminals  on  the  back  of  the  switch  and  the  other  terminal  on  the  switch 
is  grounded.  The  ignition  is  locked  when  the  switch  lever  is  in  the 
"OFF"  position.  When  in  this  position,  the  switch  lever  may  be 
taken  out,  preventing  the  operation  of  the  magneto. 

126.  The  Splitdorf  Aero  Magneto. — The  'Aero  high-tension  magneto, 
Fig.  277,  resembles  very  closely  the  Dixie  magneto,  of  which  it  may  be 

14 


210 


AUTOMOTIVE  IGNITION  SYSTEMS 


said  to  be  the  outgrowth  since  the  principle  of  operation  of  the  Dixie 
magneto  has  been  modified  and  improved  upon  in  the  Aero  magneto. 
The  principal  changes  made  in  the  Aero  magneto,  as  contrasted  with  the 
Dixie  magneto,  are  in  the  rotor  and  in  the  shape  of  the  pole  pieces.  The 
rotor  of  the  Aero  magneto  for  four-,  six-,  and  eight-cylinder  engines  has 
four  lobes  or  shoes,  as  shown  in  Fig.  278,  while  the  Dixie  rotor  has  but 


FIG.  278. — Rotating  poles,  bearings,  and  field  of  Aero  Magneto. 

two  lobes,  Fig.  269.  The  difference  in  the  pole  pieces  may  be  noticed 
by  comparing  Fig.  279  and  Fig.  280,  with  Figs.  270-273.  The  pole 
pieces  in  the  Aero  magneto  do  not  extend  completely  around  the  rotor  as 
in  the  Dixie  magneto,  but  are  confined  to  the  upper  quarters  of  the  circle. 
The  Aero  magneto  generates  four  current  impulses  in  the  primary 
winding  per  revolution  of  the  rotor.  However,  only  one-half  of  these 

current  impulses  are  used  to  produce  a  spark 
at  the  spark  plug.  The  current  wave  of  the 
Aero  magneto  is  very  similar  to  the  wave 
shown  in  Fig.  258,  where  it  will  be  seen  that 
of  the  four  current  impulses  produced  per 
revolution  of  the  rotor,  two  are  drawn 
above  the  axis  and  two  are  drawn  below 
the  axis.  The  impulses  above  the  axis  are 
called  positive  loops  and  indicate  that  the 
current  is  flowing  in  a  given  direction 
through  the  circuit.  The  impulses  below 
the  axis  are  called  negative  loops  and  in- 
dicate that  the  current  is  flowing  in  the 
opposite  direction  through  the  circuit.  The 
high-tension  surges  of  current  produced  in  the  secondary  circuit  by  the 
opening  of  the  breaker  points  also  reverse  in  direction,  so  that  the  high- 
tension  current  will  jump  from  the  center  electrode  of  the  spark  plug 
to  the  shell  at  one  spark,  and  from  the  shell  to  the  center  electrode  at  the 
next  spark.  In  the  Aero  magneto,  the  breaker  points  open  only  on  the 
positive  loops,  thus  creating  current  surges  only  in  one  direction  in  the 
high-tension  circuit. 


279 


280 


FIGS.  279  and  280.— Reversal 
of  magnetic  flux  through  the  coil 
in  Aero  magneto. 


MODERN  HIGH-TENSION  MAGNETOS  211 

With  this  construction,  the  high-tension  current  produced  in  the 
secondary  winding  and  delivered  to  the  spark  plugs  is  uniform;  that  is, 
the  high-tension  current  from  the  magneto  to  the  spark  plugs  flows  in  one 
direction  only  and  this  direction  is  such  that  the  current  always  jumps 
from  the  shell  to  the  center  electrode.  The  manufacturers  claim  that 
this  constant  direction  of  the  spark  insures  a  spark  of  great  intensity, 
uniformity,  and  superior  igniting  power. 

The  operation  of  the  rotor  in  changing  the  direction  of  the  magnetic 
flux  through  the  core  of  the  coil  is  shown  in  Fig.  279  and  Fig.  280.  In 
Fig.  279  the  magnetic  flux  goes  in  one  direction  through  core  5.  When 
wing  N  is  opposite  3,  flux  goes  through  3  and  5  to  4,  back  to  wing  S  of 
opposite  polarity.  Until  the  wing  N  has  passed  the  leaving  pole  piece  3, 
the  action  of  the  cam  holds  the  platinum  contacts  of  the  breaker  apart, 
thereby  preventing  current  from  being  induced  in  the  primary  winding 


FIG.  281. — -Aero  magneto  with  distributor  block  and  interrupter  cover  removed. 

on  core  5,  leaving  the  core  free  from  magnetic  interference  and  preparing 
it  for  a  powerful  magnetic  and  electrical  action  when  the  polarity  of  the 
field  structure  and  core  is  reversed  upon  further  rotation. 

In  Fig.  280,  the  magnetic  flux  goes  in  the  reverse  direction  through 
core  5.  Wing  N  has  now  moved  over  to  4  and  the  direction  of  the  flux 
is  reversed,  going  from  4  through  5  to  3.  When  wing  S  passes  the  leaving 
pole  piece  3,  the  action  of  the  cam  separates  the  platinum  contacts  of  the 
circuit  breaker,  thus  breaking  the  primary  circuit.  The  four  wings  of 
the  rotor  are  alternately  of  north  and  south  polarity.  When  the  wings 
of  north  polarity  pass  the  field  poles,  the  platinum  contacts  remain 
separated;  this  prevents  the  production  of  primary  current.  At  the 
same  time  the  magnetism  of  the  field  poles  and  the  core  of  the  winding 
are  brought  to  a  state  of  absolute  zero,  after  which  the  contact  points 
come  together.  When  the  wings  of  south  polarity  pass  the  field  poles, 
thus  cutting  the  magnetic  lines  of  force,  the  contacts  are  separated  at 


212  AUTOMOTIVE  IGNITION  SYSTEMS 

the  moment  of  greatest  magnetic  intensity  in  the  core  of  the  winding — 
once  in  180° — and  the  unidirectional  high-tension  current  is  carried  to 
the  spark  plug. 

The  Aero  magneto  with  distributor  block  and  interrupter  cover 
removed  is  shown  in  Fig.  281.  The  contact  points  and  interrupter  lever 
are  mounted  on  the  inside  of  the  breaker  housing.  The  cam  is  carried  by 
the  rotor  shaft  and  has  two  lobes  breaking  the  primary  circuit  every 
180°  of  rotation  of  the  shaft.  The  contact  points  may  be  adjusted  while 


21 
20 


14    13  12    11     10     9 


Front  View  Parts 

1.  Distributor  Gear.  13.  Cam  Screw. 

2.  Distributor  Brush.  14.  Lock  Washer  for  Ground  Stud  Nut. 

3.  Distributor  Finger  Screw.  15.  Washer  for  Ground  Studs. 

4.  Distributor  Finger.  16.   Cam. 

5.  Finger  Spring  for  Breaker  Bar.  17.   Distributor  Block. 

6.  Breaker  Bar.  18.  Thumb  Nut  for  Distributor  Block. 

7.  Lock  Screw  for  Platinum  Point.  19.  Breaker  Base. 

8.  Platinum  Contact  Screw.  20.  Breaker  Bar  Spring. 

9.  Breaker  Cover.  21.  Side  Plate. 

10.  Ground  Stud.  22.  Side  Plate  Stud. 

11.  Thumb  Nut  for  Ground  Stud.  23.  Magnet  Cover. 

12.  Contact  Screw  Bracket. 

FIG.  282. — Aero  magneto. 

the  magneto  is  running,  similar  to  the  manner  shown  in  Fig.  275.  The 
contact  points  should  separate  .020  in.  or  J^o  m-  when  the  fiber  block  on 
the  interrupter  arm  is  on  the  highest  part  of  the  cam.  The  circuit  dia- 
gram of  the  Aero  magneto  is  the  same  as  that  for  the  Dixie  magneto,  Fig. 
274.  Figure  282  and  Fig.  283  show  the  Aero  magneto  with  many  of  the 
parts  designated.  The  resemblance  to  the  Dixie  magneto  is  quite  marked. 
Figure  284  is  a  side  view  of  the  Aero  magneto  showing  the  points 
requiring  oiling.  The  frequency  of  oiling  depends  upon  the  nature  of  the 


MODERN  HIGH-TENSION  MAGNETOS 


213 


service  to  which  the  magneto  is  subjected.  In  general,  it  may  be  stated 
that  the  magneto  should  be  oiled  at  A  with  four  drops  of  light  oil  every 
20  hours  of  operation;  at  B  with  two  drops  of  light  oil  every  20  hours  of 
operation;  and  at  C  one  drop  of  light  oil  should  be  applied  to  the  bearing 
of  the  breaker  arm  with  a  toothpick  every  200  hours  of  operation.  Fig- 
ure 285  shows  the  breaker  base  and  the  hole  for  oiling  the  breaker  arm 
bearing.  Every  possible  precaution  should  be  taken  to  prevent  oil 


43       44 


24  25  26      27 


Side  View  Parts 


1.  Condenser. 

2.  Magnet. 

3.  Gap  Protector. 

4.  Oil  Hole  Coyer,  Front. 

5.  Screw  for  Distributor  Block. 

6.  Thumb  Nut  for  Ground  Stud. 

7.  Ground  Stud. 

8.  Screw  and  Washer  for  Fastening  Breaker. 

9.  Screw  and  Washer  for  Fastening  Condenser 
and  Primary  Lead  to  Winding. 

10.  Screw    and    Washer    for    Fastening    Primary 
Lead  Tube  Clamp. 

11.  Primary  Lead  Tube. 


12.  Primary  Lead  Tube  Clamp. 

13.  Screw  and   Washer  for  Fastening  Ground 
Clip  to  Pole  Structure. 

14.  Rotor  Shaft. 

15.  Shaft  Nut. 

16.  Woodruff  Key. 

17.  Back  Plate. 

18.  Oil  Hole  Cover,  Back. 

19.  Ground  Clip. 

20.  Screw  and  Washer  for  Fastening  Winding 
to  Pole  Structure. 

21.  High-tension  Winding. 


FIG.  283. — Aero  magneto. 

from  getting  on  the  platinum  points  as  this  would  result  in  flashing  at 
the  contact  points  when  running,  and  consequent  misfiring  of  the  engine. 

The  operation  of  the  magneto  is  controlled  by  the  magneto  or  ground 
switch,  Fig.  286.  In  the  "ON,"  or  .running  position,  the  primary  cur- 
rent is  completed  through  the  circuit  breaker,  and  sparks  are  produced 
at  the  plugs.  In  the  "OFF"  position,  the  primary  current  is  grounded 
and  ignition  prevented.  The  insulated  post  on  this  switch  should  be 
connected  to  the  terminal  on  the  breaker  cover  of  the  magneto.  The  switch 
itself  is  grounded  through  the  metal  dash  on  which  it  is  mounted.  In 


214 


AUTOMOTIVE  IGNITION  SYSTEMS 


case  the  switch  is  mounted  on  a  wooden  support,  a  ground  wire  should 

be  run  from  one  of  the  screws  or  bolts  holding  the  switch  in  position 

to  some  convenient  nut  or  bolt  on  the  engine. 

127.  The  Splitdorf  Aero  Magneto  with  Impulse  Starter. — Figure  287 

shows  the  Splitdorf  Aero  model  448  four-cylinder  magneto  fitted  with 

the  Splitdorf  impulse  starter.  This 
equipment  facilitates  the  starting 
of  hand-cranked  engines  direct  from 
the  magneto.  As  in  other  impulse 


FIG.  284. — Side  view    of    Aero    mag- 
neto showing  points  to  be  oiled. 


FIG.  285. — Point  for  oiling  breaker  arm 
on  Aero  magneto. 


starters,  this  device  permits  the  production  of  a  strong  magneto  spark 
at  the  lowest  possible  cranking  speed,  or  in  other  words,  the  action  of  the 
impulse  starter  may  be  compared  to  cranking  the  engine  at  about  500 
turns  per  minute.  A  housing,  Fig.  288,  at  the  drive  end  of  the  magneto 


FIG.    286. — Aero    magneto    control 
switch. 


FIG.  287. — Aero  Model  448  magneto  fitted  with 
impulse  starter. 


contains  the  operating  parts  of  the  impulse  starter,  and  a  small  lever  pro- 
jects from  the  housing  for  the  purpose  of  engaging  the  mechanism.  Figure 
289  shows  the  rear  view  of  the  magneto  with  the  impulse  starter 
cover  removed.  Figure  290  is  a  sectional  view  of  the  starter,  showing 
details  of  construction  and  operation.  The  member  A  is  keyed  to  the 


MODERN  HIGH-TENSION  MAGENTOS 


215 


drive  shaft  of  the  magneto  and  contains  the  notches  C  and  D.     The  pawl 

E  carries  projections  F  and  G,  and  is  movable  about  the  axis  H.     The 

cam  member  J  has  two  cams,  K  and  L,  and  also  carries  the  trip  lever  M . 

When  the  engine  is  being  started,  the  parts  of  the  starting  mechanism 


FIG.  288. — Rear   view   of   Aero    magneto 
showing  impulse  starter. 


FIG.  289. — Rear  view  of  Aero  magneto  with 
impulse  starter  cover  removed. 


rotate  at  low  speed  and  the  centrifugal  force  is  not  sufficient  to  throw  the 
trip  lever  M  out  from  the  center;  hence,  the  point  N  of  the  lever  engages 
with  the  projection  G  of  the  pawl  and  causes  projection  F  to  engage  with 
notches  C  and  D. 


FIG.  290. — Sectional  view  of^Aero  impulse  starter. 

The  member  A  is  now  prevented  from  turning,  but  cam  member  J 
continues  to  turn  and  compresses  the  coil  spring  U  inside  of  A  until  cam 
K  or  L  releases  the  projection  F.  The  coil  spring  then  causes  the  member 
A  to  rotate  at  high  speed,  carrying  the  magneto  shaft  with  it,  and  produc- 
ing a  strong  spark  in  the  cylinder.  This  spark  always  occurs  several 


216  AUTOMOTIVE  IGNITION  SYSTEMS 

degrees  past  the  upper  dead  center,  regardless  of  whether  the  spark  lever 
is  advanced  or  retarded,  thus  making  the  starter  safe. 

The  pawl  projection  F  continues  to  engage  in  notches  C  or  D  until 
the  speed  reaches  150-200  r.p.m.,  at  which  speed  the  blow  from  the  cam 
is  sufficient  to  throw  the  pawl  E  against  the  stop  X,  to  an  inoperative 
position.  At  this  speed,  the  trip  lever  M  is  thrown  out  by  centrifugal 
force,  so  that  it  no  longer  engages  with  pawl  projection^.  This  permits 
the  engine  to  throttle  down  to  idling  speeds  without  the  trip  lever  engag- 
ing. The  lever  P  on  the  side  of  the  housing  is  provided  in  order  that  the 
pawl  E  may  be  engaged  by  hand  if  necessary.  The  stop  X  is  adjustable; 
moving  it  to  the  right  permits  the  starter  mechanism  to  come  in  or  function 
at  lower  speed. 

Figure  291  shows  the  coil  springs  used  with  the  impulse  starter  and 
also  the  method  of  inserting  a  new  spring.  The  longer  spring  is  the  main 
spring  and  the  one  which  is  compressed  by  the  action  of  the  starter,  con- 
sequently driving  the  magneto  shaft  forward  at  the  proper  moment. 

On  account  of  the  strenuous  service  to 
which  this  spring  is  subjected,  it  sometimes 
breaks  and  must  be  replaced.  A  new 
spring  can  be  easily  inserted  by  putting  a 
nail  or  pin  through  the  opening  in  the  side 
of  the  housing  in  the  lateral  hole  of  mag- 
neto member  A}  the  ends  of  the  spring 
being  inserted  in  the  recess  first.  The 
middle  section  can  then  be  pressed  in  with 
ease.  The  smaller  spring  is  provided  as  a 
cushion  to  take  up  the  shock  or  jar  pro- 
duced by  the  rapid  action  of  the  mechanism. 
Care  should  be  taken  never  to  throw  the  impulse  starter  into  action  when 
the  engine  is  running,  as  grave  damage  may  result  to  the  operating  parts. 
128.  The  Aero  Magneto  with  Battery  Starting  Connections. — The 
Aero  magneto  may  be  furnished  with  two  terminals  on  the  breaker  cover, 
the  second  terminal  being  for  the  purpose  of  admitting  battery  current 
to  the  primary  winding  for  starting.  When  so  equipped,  the  four-cylinder 
magneto,  Fig.  292,  is  known  as  model  449. 

By  introducing  battery  to  the  primary  winding  on  the  magneto,  it  is 
possible  to  obtain  hot  sparks  when  the  magneto  is  making  as  low  as  5  to 
10  revolutions  per  minute.  This  introduction  of  the  battery  current 
facilitates  the  starting  of  the  engine  under  difficult  conditions  and  does  not 
interfere  with  the  regular  operation  of  the  magneto  in  any  Way.  The 
wiring  diagram  for  this  arrangement  is  given  in  Fig.  293.  The  terminal 
marked  M  is  connected  to  the  insulated  terminal  on  the  starting  motor. 
This  allows  the  battery  current  to  flow  through  the  primary  winding  of 
the  magneto  when  the  starting  switch  is  closed.  Whenever  the  engine  is 


MODERN  HIGH-TENSION  MAGNETOS 


217 


being  started  by  the  electric  self-starting  equipment,  the  battery  sends 
current  through  the  magneto  windings,  producing  sparks  the  moment  the 
engine  turns  over.  When  the  starting  switch  is  released,  the  end  of 
the  primary  magneto  winding  which  is  usually  grounded  becomes 
grounded  through  the  starting  motor  and 
the  magneto  operates  in  the  usual  way. 
The  primary  current  flowing  through 
these  connections  is  of  low  voltage. 
The  terminal  marked  G  is  connected  to 
the  magneto  control  switch  for  the  pur- 
pose of  cutting  off  the  ignition  to  stop 
the  engine.  It  is  very  essential  that  all 
connections  be  kept  clean  and  tight. 

129.  The  Aero  Magneto  for  Eight- 
cylinder  Engines. — The  Aero  magneto 
shown  in  Fig.  294,  for  eight-cylinder  auto- 
mobile engines,  has  a  f  our-lobed  rotor  and 
produces  two  sparks  per  revolution  of  the 
magneto  shaft.  This  requires  that  the 
magneto  be  driven  at  twice  crankshaft  speed  to  produce  the  four  sparks 
needed  for  each  revolution  of  the  engine.  The  distributor  is  driven  from 
the  magneto  shaft  by  a  2  to  1  gear  reduction.  The  eight-cylinder  dis- 
tributor, Fig.  295,  differs  from  the  usual  distributor  in  having  the  seg- 


FIG.  292. — Aero  model  449  magneto 
for  battery  starting. 


FIG.  293. — Wiring  diagram  of  Aero  magneto  with  battery  starting. 

ments  arranged  in  two  rows  of  four  segments  each,  instead  of  in  one  row. 
of  eight  segments.  This  construction  permits  of  a  very  compact  group- 
ing of  the  distributor  parts.  The  rotor,  Fig.  296,  has  a  double  ringer 
which  makes  contact  with  the  two  rows  of  segments. 


218 


AUTOMOTIVE  IGNITION  SYSTEMS 


The  high-tension  current  from  the  secondary  winding  is  collected 
by  brush  C,  Fig.  296,'  which  bears  upon  a  brass  plate  on  the  coil  as- 
sembly. This  brass  plate  is  the  terminal  of  the  secondary  winding, 
and  the  brush  C  makes  contact  with  this  plate  in  all  positions  of  spark 


FIG.  294. — Aero  magneto  for  eight-cylinder     FIG.  295. — Aero  eight-cylinder  distributor, 
engines. 

advance.  The  high-tension  current  is  conducted  through  the  center 
of  the  rotor  to  brush  D;  then  by  means  of  the  sector  S  in  the  distributor 
block,  Fig.  295,  the  current  is  conducted  to  either  of  the  two  brushes, 
Al  or  Bl.  Brushes  Al  and  Bl  are  connected,  respectively,  to  brushes 
A2  and  B2.  Brushes  A 2  and  B2  make  contact 
with  the  distributor  segments  in  the  distributor 
block  from  which  the  cables  lead  to  the  spark 
plugs.  The  brushes  Al  and  Bl  are  placed 
alternately  in  electrical  contact  with  the  brush 


SL 


FIG.  296. — Aero  eight-cylinder  FIG.  297. — Aero  twelve-cylinder  magneto, 

rotor. 

D.  They  become  alive  only  at  the  moment  when  their  companion 
brushes,  A 2  and  B2,  are  actually  in  contact  with  a  segment  in  either  of 
the  two  rows  of  segments  on  the  distributor  block.  This  arrangement 
makes  it  impossible  for  the  spark  to  jump  to  the  wrong  segment.  A 
spark  received  at  any  post  of  the  inner  row  of  the  distributor  block 


MODERN  HIGH-TENSION  MAGNETOS  219 

will  be  followed  by  a  spark  from  a  post  in  the  outer  row  of  the  block, 
which  is  180°  away  from  the  post  of  the  previous  spark. 

130.  The  Aero  Magneto  for  Twelve -cylinder  Engines. — The 
Aero  magneto  for  twelve-cylinder  automobile  engines,  shown  in  Fig. 
297,  has  a  six-lobed 'rotor  and  gives  three  sparks  per  revolution  of  the 
magneto  shaft.  It  is  driven  at  twice  crankshaft  speed  to  furnish  the 
six  sparks  needed  per  revolution  of  the  twelve-cylinder  engine.  The 
distributor,  Fig.  298,  which  consists  of  two  rows  of  six  segments  each 
moulded  together  in  the  distributor  block,  is  driven  at  one-half  the 
speed  of  the  magneto  shaft.  The  twelve-cylinder  rotor,  Fig.  299,  is 
very  similar  to  the  eight-cylinder  rotor,  the  only  difference  being  in 
the  size,  and  in  the  angularity  of  the  brushes.  In  the  twelve-cylinder 
model,  a  spark  in  the  outer  row  of  segments  is  followed  by  a  spark  in 
the  inner  row  of  segments  at  a  post  displaced  120°  from  the  post  of  the 
first  spark.  . 


FIG.  298. — Aero  twelve-cylinder  FIG.  299. — Aero  twelve-cylinder 

distributor.  rotor. 

131.  The  Aero  Airplane  Magneto. — The  Aero  magneto,  as  devel- 
oped for  airplane  use,  is  shown  in  Fig.  300.  The  construction  differs 
somewhat  from  that  of  the  other  Aero  magnetos  which  have  been 
described,  chiefly  in  the  arrangement  of  the  distributor  and  in  the  shape 
of  the  magnets.  The  segments  of  the  distributor  are  all  in  one  row 
and  the  distributor  rotor  has  but  one  finger  or  brush  which  makes  con- 
tact with  the  distributor  segments.  The  interior  view  of  the  eight- 
cylinder  airplane  magneto,  model  825,  is  shown  in  Fig.  301.  This 
illustration  shows  the  magnets  of  the  airplane  models  to  be  square  in 
shape  instead  of  having  a  circular  bend  as  in  the  automobile  type. 
The  design  of  the  breaker  box  has  been  changed  to  provide  for  the 
increased  size  of  the  parts  needed  in  airplane  service.  The  terminal 
shown  on  the  side  of  the  magneto  in  Fig.  301  is  provided  for  tapping 
off  current  from  the  magneto  for  use  in  wireless  telegraphy. 

An  interesting  method  is  employed  in  getting  high-tension  current 
for  starting.  At  the  ordinary  cranking  speed  of  airplane  engines,  the 


220 


AUTOMOTIVE  IGNITION  SYSTEMS 


magneto  is  revolved  too  slowly  to  give  a  good  igniting  spark.  In  the 
Aero  airplane  ignition  system,  a  second  high-tension  magneto  known 
as  model  100  is  provided  for  cranking.  Figure  302  shows  model  100 
and  model  825  eight-cylinder  magnetos  as  they  are  used  on  airplane 
engines.  The  auxiliary  starting  magneto  may  be  turned  by  hand  by 


FIG.  300. — Aero   model  825  airplane 
magneto. 


FIG.  301. — Interior  view  of  Aero  model 
825  magneto. 


the  small  crank,  or  it  may  be  connected  by  gearing  to  the  starting  crank  of 
the  engine.  In  the  first  case,  an  attendant  turns  the  starting  magneto 
while  the  engine  is  being  cranked.  In  the  second  case,  the  cranking  of 
the  engine  automatically  turns  the  starting  magneto  at  a  high  rate  of 
speed.  The  starting  magneto  generates  four  sparks  per  revolution  of  the 


FIG.  302. — Aero  model  100  starting  magneto  with  model  825  airplane  magneto. 

magneto  shaft.  These  sparks  are  introduced  to  the  distributor  of  the 
regular  magneto  and  from  there  are  sent  to  the  spark  plug  in  that  engine 
cylinder  which  happens  to  be  in  the^firing  position  at  that  instant.  The 
use  of  the  starting  magneto  thus  gives  a  stream  of  high-tension  sparks 
in  the  cylinder  of  the  engine.  The  heating  effect  of  the  several  sparks 


MODERN  HIGH-TENSION  MAGNETOS 


221 


which  occur  in  each  cylinder  is  such  that  the  gas  in  the  cylinder  is  readily 
exploded  and  the  engine  starts  quickly.  As  soon  as  the  engine  fires  and 
comes  up  to  speed,  the  regular  magneto  takes  up  its  work  and  the 
starting  magneto  is  stopped. 


CONTROL  SWITCH 


Dixie  too  H.T.  STARTING  MAGNETO 

OPERATED  FROM  MOTOR. 

CRANK  HANC-E. 


FIG.  303. — External  wiring  diagram  of  Aero  model  800  ignition  system  for  aircraft  with 

hand  starting  magneto. 


FIG.  304. — Internal  wiring  diagram  of  Aero  aircraft  type  magneto. 

Figure  303  is  the  external  wiring  diagram  of  the  system  applied  to  an 
eight-cylinder  airplane  engine.  Two  main  magnetos  are  employed,  each 
having  a  set  of  spark  plugs  in  the  engine.  The  magneto  control  switch 


222  AUTOMOTIVE  IGNITION  SYSTEMS 

is  arranged  so  that  either  or  both  of  the  main  magnetos  may  be  used  for 
ignition.  When  both  are  used,  the  gas  in  the  cylinder  is  ignited  from  two 
widely  separated  plugs,  resulting  in  a  quicker  burning  of  the  gas  and  a 
more  powerful  and  speedy  engine.  The  starting  magneto  is  connected 
to  but  one  of  the  main  magneto  distributors.  The  figure  shows  the  hand- 
turned  starting  magneto  and  also  the  method  of  driving  it  from  the  start- 
ing crank.  The  internal  wiring  diagram  of  the  Aero  magneto  is  shown 
in  Fig.  304. 

132.  Aero  Magneto  Adjustments. — The  timing  of  the  Aero  magneto  is 
taken  care  of  by  the  adjusting  of  the  breaker  points  and  the  setting  of 
the  rotor  edge  distance.  The  airplane  types  also  have  the  additional 
adjustment  of  the  distributor  finger  or  brush. 

As  in  all  magnetos,  the  breaker  points  of  the  Aero  magneto  should 
separate  at  the  instant  the  spark  is  desired  in  the  cylinder.  Before  this 


FIG.  305. — Buzzer  test  set  for  setting  rotor  edge  distance. 

adjustment  can  be  made,  the  rotor  edge  distance  should  be  checked  and 
adjusted.  This  can  be  accomplished  by  the  use  of  a  thickness  gage  and 
a  buzzer  test  set. 

A  buzzer  test  set  is  shown  in  Fig.  305.  It  consists  of  a  case  containing 
two  dry  cells  with  an  electric  buzzer  mounted  on  the  top.  The  buzzer  is 
connected  to  the  dry  cells,  and  the  circuit  is  brought  to  the  two  binding 
posts  at  the  top  of  the  case.  Any  metallic  connection  between  the  two 
binding  posts  will  operate  the  buzzer. 

The  magnet  cover,  magnets,  winding,  rotor  cover,  breaker  cover,  and 
condenser  should  be  removed  from  the  magneto  whose  edge  distance  is 
to  be  tested.  A  lead  should  be  run  from  one  of  the  binding  posts  on  the 
buzzer  set  to  the  post  that  is  fastened  to  the  contact  screw  bracket  of 
the  magneto,  and  another  lead  should  be  run  from  the  other  binding  post 
on  the  buzzer  set  to  the  post  extending  from  the  breaker  base.  These 


MODERN  HIGH-TENSION  MAGNETOS  223 

leads  are  shown  in  place  in  Fig.  306.  The  rotor  shaft  should  be  turned 
in  the  direction  indicated  by  the  arrow  on  the  drive  end  plate  until  the 
buzzer  does  not  vibrate.  The  shaft  should  be  held  in  this  position  and 
the  distance  of  the  rotor  from  the  field  pole  checked ;  this  distance  should 
be  from  .050  in. to  .075  in.  This  distance  is  measured  between  the  field 
pole  and  the  rotor  lobe  that  is  leaving  and  not  the  one  that  is  approaching 
the  pole. 

If  this  distance  is  not  within  the  limits  mentioned  above,  the  three 
slotted  round  nuts  that  hold  the  breaker  to  the  magneto  should  be 
loosened  and  the  breaker  turned  to  the  right  or  to  the  left  until  the  proper 
edge  distance  is  obtained.  The  three  nuts  should  be  tightened  securely 
and  the  edge  distance  rechecked.  If  correct,  the  cupped  washer  should  be 
staked  in  the  slots  in  the  nuts. 


FIG.  306. — Setting  rotor  edge  distance  on  Aero  magneto. 

After  the  rotor  edge  distance  has  been  properly  adjusted,  the  breaker 
points  should  be  adjusted  to  open  .018  in.  to  .022  in.  when  the  highest 
point  of  the  breaker  cam  is  in  contact  with  the  fiber  bumper  on  the 
breaker  arm.  The  rotor  edge  distance  should  be  rechecked  again  and, 
if  found  correct,  the  magneto  may  be  reassembled. 

The  adjustment  of  the  distributor  brush  in  the  airplane  magneto  is 
made  necess.ary  because  of  the  introduction  of  the  high-tension  current 
from  the  starting  magneto  at  this  point.  The  carbon  brush  should  be 
entirely  on  the  segment,  when  the  breaker  points  open,  but  it  should  not 
be  so  far  on  the  segment  that  the  rear  edge  of  the  brush  is  further  than 
%6  in.  from  the  edge  of  approach  of  the  segment.  The  carbon  brush 
should  not  overlap  the  segment;  if  it  does,  the  brush  should  be  beveled 


224 


AUTOMOTIVE  IGNITION  SYSTEMS 


to  the  edge  of  the  segment.     This  adjustment  is  pictured  in  Fig.  307. 
The  small  views  at  the  side  show  the  proper  condition. 

Where  two  magnetos  are  used  on  the  same  engine,  one  of  them  should 
be  adjusted  so  that  the  firing  point  conforms  to  the  setting  recommended 
by  the  manufacturer  of  the  engine.  The  other  magneto  should  then  be 
synchronized  with  the  first  so  that  both  magnetos  will  produce  sparks 


FIG.  307. — Setting  the  distributor  brush  on  Aero  magneto. 

at  exactly  the  same  instant.  This  synchronizing  should  be  made  by 
means  of  adjustable  couplings  and  not  by  the  adjustment  of  the  breaker 
points  of  the  magneto.  This  adjustment  should  be  checked  at  frequent 
intervals  since  the  advantage  of  having  two  points  of  ignition  in  each 
cylinder  is  lost  if  the  two  sparks  occur  as  much  as  ;Ko>ooo  of  a  second 
apart. 


CHAPTER  IX 
CARE  AND  REPAIR  OF  IGNITION  APPARATUS 

133.  Methods  of  Mounting  Ignition  Apparatus. — Ignition  equipment 
must  always  be  driven  at  some  definite  gear  ratio  to  the  engine.  This  is 
accomplished  by  driving  the  apparatus  by  a  chain  or  gears  from  the 
crankshaft  of  the  engine.  The  number  of  teeth  on  the  sprockets  or  gears 
is  such  that  the  proper  gear  reduction  is  obtained.  The  four-stroke 
cycle  engine  requires  an  explosion  in  each  cylinder  every  two  revolutions 


STARTING  MOTOR 


GENERATOR 


FIG.  308. — Ford  engine  showing  location  of  timer. 

of  the  crankshaft;  thus  every  cylinder  on  the  engine  is  fired  during  two 
complete  revolutions  of  the  crankshaft.  The  order  in  which  the  cylinders 
fire  is  called  the  "  firing  order  "  of  the  engine.  The  timer  or  the  distributor 
directs  the  current  so  that  each  cylinder  gets  a  spark  in  the  proper  order. 
The  Vibrating  Coil-timer  System. — A  typical  example  of  this  type  of 
ignition  system  is  that  installed  on  the  Ford  engine.  The  timer  is 
located  at  the  front  end  of  the  engine,  as  shown  in  Fig.  308,  and  is  driven 
by  an  extension  of  the  camshaft.  With  the  exception  of  the  low-tension 
magneto,  the  timer  is  the  only  moving  part  of  the  Ford  ignition  system. 
The  magneto,  however,  simply  acts  as  a  source  of  low-tension  current  for 
the  ignition  system  and  has  nothing  to  do  with  the  distribution  of  current. 
In  fact,  the  magneto  may  be  replaced  by  an  electric  battery,  either  dry 
cells  or  storage,  and  the  system  will  function  the  same  as  before.  The 
io  225 


226 


AUTOMOTIVE  IGNITION  SYSTEMS 


low-tension  current  is  conducted  from  the  timer  terminals  to  the  four 
vibrating  coils  mounted  on  the  dash.  The  high-tension  current  gen- 
erated in  the  coils  is  taken  to  the  spark  plugs  in  the  cylinders  by  heavily 
insulated  high-tension  cables. 

The  Non-vibrating  Coil  Distributor  System.— In.  the  battery  ignition 
systems  employing  a  single  non-vibrating  coil  with  a  distributor  in  the 
high-tension  circuit  to  direct  the  high-tension  current  to  the  proper  spark 
plugs,  the  distributor  must  be  driven  at  one-half  crankshaft  speed.  The 
cam  operating  the  interrupter  is  usually  mounted  on  the  distributor 
shaft  and  has  as  many  points  as  there  are  cylinders  on  the  engine.  The 
interrupter  and  distributor  unit  is  mounted  vertically  and  driven  by 
"one  to  one"  gears  from  the  camshaft  of  the  engine.  Figure  309  shows 
the  Delco  ignition  system  as  installed  on  the  Nash  Six  engine.  The  igni- 


GENERATOR 


FIG.  309. — DeLco  ignition  unit  on  Nash  Six. 

tion  unit,  consisting  of  the  interrupter  and  distributor,  is  shown  on  the 
side  of  the  engine.  The  shaft  of  the  unit  extends  down  into  the  crank 
case  of  the  engine.  At  the  lower  end  of  this  shaft  is  a  spiral  gear  which 
meshes  with  a  spiral  gear  of  the  same  size  carried  by  the  camshaft.  The 
high-tension  cables  leading  from  the  distributor  to  the  spark  plugs  are 
placed  in  the  metal  tube  shown  passing  around  to  the  left  of  the  engine 
cylinder  block.  The  non-vibrating  coil  and  the  ignition  control  switch 
are  mounted  on  the  dash. 

Another  common  method  of  mounting  the  interrupter-distributor 
ignition  unit  is  shown  in  Fig.  310.  The  ignition  unit  is  carried  at  one 
end  of  the  electrical  generator  and  is  driven  by  spiral  gears  from  the  gen- 
erator shaft.  The  generator  in  turn  is  driven  by  the  train  of  gears  in 
the  timing  gear  case  of  the  engine.  The  engine  is  shown  with  the  timing 


CARE  AND  REPAIR  OF  IGNITION  APPARATUS        227 


FIG.  310. — Case   continental   engine   showing   Westinghouse   ignition   unit   mounted   on 

generator. 


FIG.  311. — Magneto  installation  on  Packard  Model  E  truck  engine. 


228 


AUTOMOTIVE  IGNITION  SYSTEMS 


gear  case  cover  removed.  The  lower  gear  is  mounted  on  the  crankshaft 
of  the  engine;  the  large  gear  above  is  the  camshaft  gear;  the  small  gear 
to  the  left  is  the  generator  and  pump  shaft  gear.  The  crankshaft  gear 
has  36  teeth ;  the  generator  gear  has  24  teeth ;  consequently,  the  generator  is 
driven  at  1J^  times  crankshaft  speed.  The  ignition  unit  must  revolve  at 
one-half  crankshaft  speed,  and,  therefore,  has  a  3  to  1  reduction  at  the  spiral 
gears  on  the  distributor  and  generator  shafts. 

Other  methods  of  mounting  the  distributor  unit  are  shown  in  Figs. 
89,  102,  156,  160,  163,  and  167.  A  study  of  these  illustrations  will 
indicate  the  method  of  obtaining  the  convenient  mounting  and  correct 
gear  reduction  required  for  this  class  of  ignition  equipment. 


FIG.  312. — Chain  driven  magneto  on  Continental  engine  used  on  the  3)^  ton  Oneida  truck. 


Magneto  Drives. — The  magneto  is  usually  mounted  with  the  shaft 
horizontal  and  is  driven  by  a  gear  meshing  with  the  camshaft  gear  at  the 
front  end  of  the  engine.  Figure  311  shows  the  magneto  installation  on 
the  Packard  model -E  truck  motor.  The  magneto  is  mounted  on  a 
bracket  on  the  right  side  of  the  engine  crank  case  and  is  driven  by  a  gear 
meshing  with  the  camshaft  gear  as  shown.  The  high-tension  cables  are 
protected  by  a  tubular  container.  The  only  part  of  this  ignition  system 
not  shown  is  the  control  switch  mounted  on  the  dash. 

On  some  engines,  the  magneto  is  chain  driven,  as  shown  in  Fig.  312, 
which  illustrates  the  Continental  engine  used  on  the  3^  ton  Oneida 


CARE  AND  REPAIR  OF  IGNITION  APPARATUS        229 


truck.     The  magneto  is  mounted  above  the  electrical  generator  and  is 
chain  driven  from  the  pump  shaft  which  also  drives  the  generator. 


FIG.  313. — Magneto  mounting  on  Duesenberg  engine. 

Figure  313  shows  the  magneto  mounting  on  the  Duesenberg  engine. 
The  magneto  is  driven  by  a  transverse  shaft  at  the  front  end  of  the 
engine. 

134.  Magneto  Couplings. — The  engine  is  always  provided  with  a 
bracket  to  which  the  magneto  is  fitted. 
A  suitable  shaft  drives  the  magneto. 
Due  to  the  difficulty  of  lining  up  the 
center  of  the  magneto  shaft  with  the 
center  of  the  drive  shaft,  a  flexible 
coupling  is  provided  between  the  ends 
of  the  two  shafts.  This  flexible 
coupling  allows  the  magneto  to  be 
driven  satisfactorily  even  with  the  two 
shafts  considerably  out  of  alignment. 
The  flexible  coupling  acts  as  a  universal  joint. 

A  flexible  coupling  often  used  for  magneto  drives  is  the  Oldham  coup- 
ling shown  in  Fig.  314.  The  Oldham  coupling  consists  essentially  of 
three  parts,  the  end  pieces  A  and  B  and  the  center  piece  C.  One  of  the 
end  pieces  is  fastened  to  each  of  the  two  shafts  to  be  coupled.  These 
pieces  each  have  a  slot  cut  across  their  opposing  faces.  The  center  ipece 


FIG.  314. — Oldham  flexible  coupling. 


230 


AUTOMOTIVE  IGNITION  SYSTEMS 


FIG. 


315.— Flexible 
coupling. 


disc 


C  has  two  splines,  one  on  either  side,  at  right  angles  to  each  other.  When 
the  joint  is  assembled,  the  piece  C  is  held  between  the  two  end  pieces  and 
cannot  escape.  The  power  is  readily  transmitted  through  the  three 
parts,  the  construction  of  which  permits  of  some  angularity  between 
the  two  shafts. 

A  very  efficient  type  of  magneto  coupling  is  shown  in  Fig.  315.  In 
this  coupling  each  of  the  two  shafts  to  be  joined  terminates  in  a  forked 
member.  This  member  has  a  hole  in  each  end  and  is  bolted  to  a  heavy 

leather  or  fiber  disc.  The  second  forked 
member  is  fastened  to  this  disc  at  right  angles 
to  the  first.  This  construction  permits  the 
coupling  to  accommodate  itself  to  any  angu- 
larity that  might  be  present  between  the  two 
shafts  and  at  the  same  time  the  flexible 
nature  of  the  disc  enables  the  coupling  to 
absorb  the  mechanical  shocks  which  might 
otherwise  be  transmitted  to  the  magneto  from 
the  engine.  This  coupling  needs  very  little 
attention  and  no  lubrication. 

The  Uniflex  flexible  joint,  Fig.  316,  is  also 
adaptable  for  driving  a  magneto.     The  joint 

consists  of  two  shaft  members  and  a  set  of  blocks.  The  shaft  members 
are  jawed  hubs,  so  designed  that  they -engage  with  each  other  through 
the  blocks.  The  blocks  are  built  up  of  six  sections  and  may  be  faced 
with  fiber,  wood,  or  any  other  material  used  for  magneto  drives.  When 
the  sections  are  covered  in  this  way,  the  joint  is  insulating  and  shock 
absorbing  and  requires  little  lubrication. 

135.  Bearings  and  Lubrication. — The  moving  parts  of  an  ignition 
apparatus  must  of  necessity  be  of 
light  construction  and  must  rotate 
at  high  speed.  These  parts  are, 
therefore,  provided  with  the  best 
grade  of  anti-friction  bearings. 
The  ball  bearing  lends  itself  admir- 
ably to  this  type  of  service  and  is 
generally  used,  although  some 
battery  ignition  units  have  plain  bearings  lined  with  bronze  or  other 
anti-friction  metal. 

The  magneto  armature  shaft  and  the  distributor  shaft  are  mounted 
upon  ball  bearings  as  shown  in  Fig.  317.  These  bearings  must  be 
adjusted  very  accurately  so  as  to  carry  the  shafts  exactly  in  the  cor- 
rect position.  The  clearance  between  the  armature  core  and  the  pole 
pieces  is  but  a  few  thousandths  of  an  inch;  consequently,  the  armature 
shaft  bearings  must  hold  the  armature  exactly  centered  between  the 


FIG.  316.— The  Uniflex  coupling. 


CARE  AND  REPAIR  OF  IGNITION  APPARATUS        231 


pole  pieces.  Any  departure  from  this  central  position  will  cause  the 
armature  core  to  rub  on  the  pole  pieces,  rapidly  rendering  the  magneto 
useless.  Bearings  used  for  this  service  are «  very  accurately  made, 
and  should  be  given  care  and  attention  worthy  of  their  fine  construction. 


BEARING  CONE 
RETAINING  WASHER 


BALL  BEARING  CLP 

BALL  AND  SEPARATOR 
ASSEMBLY 

x 


FIG.  317. — Sectional   view   of   magneto   showing   method   of   mounting   ball   bearings. 

Figure  318  is  a  cross  section  of  a  magneto  bearing,  showing  the  ar- 
rangement of  the  parts.     The  balls  roll  on  an  inner  race  which  is  called 
the  "cone;"  the  outer  race  is  called 
the   "cup."     The  shape  of  the  cup 
and  the  cone  permits  the  bearing  to 
take  a  certain  amount  of  side  thrust, 
preventing  any  end  play  or  side  move- 
ment of  the  armature. 

Lubrication. — The  lubrication  of 
the  bearings  of  an  ignition  apparatus 
is  very  important.  The  bearings  must 
be  supplied  with  enough  oil  to  lubri- 
cate them  properly,  but  they  must 
not  receive  an  over-supply  since  too 
much  oil  on  electrical  equipment  is 
certain  to  cause  trouble.  This  is  es- 
pecially true  of  those  parts  which 
carry  current,  such  as  the  breaker 
points  and  the  distributor  segments.  The  moving  parts  in  the  breaker 
mechanism  should  be  oiled  with  but  a  small  drop  of  thin  oil  about  once 
a  month.  The  distributor  needs  very  little  oil  carefully  applied.  It 


FIG.     318. — Cross    section    of    magneto 
ball  bearing  showing  angular  contact. 


232  AUTOMOTIVE  IGNITION  SYSTEMS 

should  be  cleaned  about  once  a  month  with  a  cloth  slightly  dampened 
with  a  good  grade  of  vaseline.  This  will  remove  any  carbon  dust  which 
may  have  been  worn  from  the  carbon  fingers  and  will  leave  a  thin  film 
of  oil  to  lubricate  the  surface  over  which  the  brush  slides. 

The  bearings  of  the  distributor  shaft  in  battery  ignition  units  and 
the  bearings  on  the  armature  shaft  of  magnetos  should  receive  a  few 
drops  of  thin  oil  about  once  each  month.  Not  more  than  a  few  drops 
should  be  applied  as  any  surplus  oil  will  find  its  way  into  the  windings 
and  other  parts  of  the  electric  circuit  and  will  destroy  the  insulation 
and  cause  short  circuits  and  other  troubles.  The  oil  holes  leading  to 
bearings  of  this  nature  are  usually  supplied  with  felt  wicks  which  will 
absorb  only  a  few  drops  of  oil;  any  additional  amount  will  simply  run 
over  the  outside  of  the  oil  cup,  and  escape.  The  wick  feeds  the  oil 
to  the  bearing  very  slowly ; over  a  long  period. 

It  may  be  said  in  connection  with  the  oiling  of  an  ignition  appara- 
tus that  a  little  oil  supplied  often  is  of  more  value  than  a  larger  quantity 
applied  at  longer  intervals.  The  care  and  attention  given  to  the  ig- 
nition apparatus  in  this  respect  will  result  in  improved  performance. 
Oil  which  contains  graphite  should  never  be  used  as  graphite  is  a  con- 
ductor of  electricity  and  will  find  its  way  into  places  where  it  will  cause 
trouble  by  short  circuits. 

136.  Impulse  Starters. — Impulse  starters  are  subjected  to  very  hard 
service.     Care  should  be  taken  to  keep  them  free  from  dirt,  and  well 
lubricated  at  all  times.     Ordinary  gas  engine  cylinder  oil,  such  as  is 
used  for  lubricating  the  engine  on  which  the  impulse  starter  is  used, 
is  excellent  for  this  purpose.     The  starter  should  be  taken  apart  oc- 
casionally, and  the  parts  cleaned  and  examined  closely  for  wear.     Any 
worn  or  defective  parts  should  be  replaced  with  new  ones.     The  springs, 
especially,  should  be  replaced  as  soon  as  any  indication  of  wear  appears. 
The  work  of  the  impulse  starter  subjects  these  springs  to  such  severe 
usage  that  one  is  apt  to  break  at  any  instant  without  previous  notice 
of  failure.     Consequently,  a  few  extra  springs  should  be  kept  on  hand. 

137.  General  Rules  for  Magneto  Timing. — The  four-stroke  cycle 
gasoline  engine  used  on  automobiles  goes  through  a  series  of  operations 
requiring  four  strokes  of  the  piston,  or  two  revolutions  of  the  crankshaft. 
Figure  319  represents  these  two  revolutions  so  as  to  show  the  position  of 
the  crank  when  the  different  events  occur.     The  diagram  is  drawn  for  a 
vertical  engine  with  the  crank  revolving  to  the  left  as  indicated  by  the 
arrow.     This  is  the  direction  of  rotation  of  an  automobile  engine  to  a 
person  standing  in  front  of  the  car  looking  toward  the  engine. 

Let  it  be  assumed  that  the  engine  piston  has  reached  the  top  of  the 
stroke  and  has  started  down  on  the  return  stroke.  The  crank  of  the 
engine  will  also  be  moving  down  until  the.crank  angle  is  approximately  10°, 
when  the  inlet  valve  opens.  The  suction  stroke  of  the  engine  then 


CARE  AND  REPAIR  OF  IGNITION  APPARATUS        233 

takes  place,  the  inlet  valve  closing  about  20°  to  30°  past  the  lower- 
dead  center.  The  inlet  valve  has,  consequently,  been  open  180°  to 
200°.  As  the  crank  moves  on,  the  gas  is  compressed,  both  valves  being 
closed.  From  5°  to  10°  before  the  upper  dead  center  is  reached,  the 
gas  is  ignited  and  the  burning  or  combustion  occurs  during  a  period 
of  from  5°  to  10°.  The  full  force  of  the  explosion  is  exerted  just  as 
the  crank  passes  the  upper  dead  center  and  the  piston  begins  to  descend. 
The  expansion  of  the  gas  now  takes  place.  From  30°  to  45°  before  the 
lower  dead  center,  the  exhaust  valve  opens,  permitting  the  gases  to  be 
forced  out  of  the  cylinder.  The  exhaust  valve  closes  a  few  degrees  past 


LOWER   DEAD 
CENTER 


FIG.  319. — Order  of  events  in  the  four-stroke  cycle  engine. 

the  upper  dead  center.     One  complete  cycle  has  now  been  completed  and 
the  engine  immediately  enters  upon  a  second  cycle. 

The  above  description  of  events  which  take  place  in  the  four- 
stroke  cycle  engine  is  for  the  normal  running  of  the  engine  after  it  has 
been  started.  While  the  engine  is  being  cranked  for  starting,  it  is  neces- 
sary that  the  ignition  point  be  delayed  until  the  piston  has  passed  the 
upper  dead  center.  This  is  because  of  the  fact  that  while  the  engine  is 
being  slowly  turned  by  hand  or  by  the  starting  equipment,  an  explosion 
in  the  cylinder  before  the  piston  has  reached  the  upper  dead  center  will 
drive  the  piston  backwards.  This  is  apt  to  injure  the  person  cranking 
the  engine,  or  damage  the  starting  mechanism.  The  ignition  point  is 
delayed  until  the  piston  has  passed  the  upper  dead  center  by  retarding 


234 


AUTOMOTIVE  IGNITION  SYSTEMS 


the  spark.  After  the  engine  is  started,  the  spark  is  advanced  until  it  is 
again  taking  place  at  the  point  shown  in  Fig.  319.  The  combustion  of 
the  mixture  of  gasoline  vapor  and  air  in  the  cylinder  does  not  take  place 
instantaneously,  as  is  commonly  believed,  but  requires  a  fraction  of  a 
second  for  its  completion.  During  this  short  interval  of  time  the  piston 
may  move  a  considerable  distance,  especially  if  the  engine  is  running  at  a 
high  speed.  It  is  for  this  reason  that  the  spark  must  take  place  a  few 


DISTRIBUTOR   ARM 

ON   NO.  I  CYLINDER 

SEGMENT          } 


FIG.  320. — Timing  the  magneto  to  the  engine. 

degrees  before  the  upper  dead  center,  as  shown  in  the  diagram,  to  allow 
time  for  the  mixture  to  burn  and  the  full  pressure  to  develop  before  the  piston 
starts  down  on  the  working  stroke.  The  faster  the  engine  is  running  the 
farther  the  spark  must  be  advanced.  An  engine  running  slowly  must 
have  a  retarded  spark.  These  conditions  require  that  the  time  of  the 
spark  in  the  cylinder  be  under  the  control  either  of  the  driver  or  of  an 
automatic  spark  advance  mechanism. 

Magnetos  installed  on  engines  must  be  adjusted  to  produce  the  spark 


CARE  AND  REPAIR  OF  IGNITION  APPARATUS        235 

in  the  cylinder  at  the  proper  instant.  This  adjustment  of  the  magneto 
is  called  timing.  Figure  320  shows  a  cross  section  of  cylinder  No.  1  on 
a  gasoline  engine  with  the  parts  in  the  proper  position  for  the  occur- 
rence of  the  spark.  The  piston  has  just  passed  the  upper  dead  center. 
The  mixture  of  gasoline  vapor  and  air  in  the  cylinder  has  been  compressed 
into  the  clearance  space  at  the  top  of  the  cylinder.  Both  valves  are  closed 
since  this  is  the  beginning  of  the  working  stroke.  With  the  engine  in  this 
position,  the  magneto  should  be  timed.  The  flexible  coupling  driving  the 
magneto  should  be  loosened  and  the  magneto  shaft  turned  in  the  direction  of 
its  normal  rotation  until  the  rotating  brush  in  the  magneto  distributor  is  on 
the  distributor  segment  marked  "No.  1."  This  is  the  segment  from 
which  the  cable  leads  to  the  spark  plug  in  cylinder  No.  1.  With  the 
spark  lever  in  the  fully  retarded  position,  the  magneto  shaft  is  turned 
slowly  until  the  contact  points  in  the  breaker  box  are  just  separating. 
The  magneto  is  held  carefully  in  this  position  while  the  coupling  is  being 
tightened.  The  other  spark  plug  cables  are  then  attached  to  the  dis- 
tributor terminals  in  the  order  of  firing  of  the  cylinders  of  the  engine. 
With  the  spark  lever  in  the  fully  retarded  position,  the  magneto  will 
deliver  a  spark  to  the  clyinder  late  enough  for  safe  cranking,  while  the 
early  spark  required  for  high  speed  operation  may  be  had  by  advancing 
the  spark  lever. 

138.  General  Rules  for  Battery  Ignition  Timing. — The  usual  form  of 
battery  ignition  used  on  most  automobile  engines  is  the  type  using  the 
single  non-vibrating  coil  with  an  interrupter  and  a  distributor.  The 
same  rules  apply  to  this  type  of  ignition  equipment  as  apply  to  the  mag- 
neto. The  engine  is  set  with  the  piston  in  No.  1  cylinder  on  the 
upper  dead  center  on  the  working  stroke.  The  distributor  shaft  is 
turned  until  the  brush  is  on  segment  No.  1  and  the  contact  points  are 
just  opening,  with  the  spark  control  lever  in  the  fully  retarded  position. 
The  distributor  drive  shaft  is  fixed  in  this  position,  either  at  the  coupling 
or  by  meshing  the  driving  gears.  The  cables  from  the  distributor  seg- 
ments are  then  attached  to  the  proper  spark  plugs,  according  to  the 
firing  order  of  the  engine,  and  the  timing  is  complete. 

Timing  the  Ford  Ignition  System. — The  timing  of  the  vibrating  multi- 
ple coil  and  timer  ignition  system  with  the  engine  is  somewhat  different 
from  the  method  employed  in  the  systems  just  described.  The  ignition 
system  used  on  the  Ford  automobile  is  a  good  example  of  this  type. 
Figure  321  shows  the  position  of  the  various  parts  when  the  Ford  ignition 
system  is  correctly  timed.  As  before,  the  engine  is  set  with  the  piston  in 
No.  1  cylinder  just  past  dead  center  at  the  beginning  of  the  working 
stroke.  The  camshaft  gears  driving  the  timer  arm  are  demeshed  and 
shifted  until,  with  the  timer  in  the  retarded  position,  the  roller  arm  is  at 
the  point  where  the  roller  is  just  making  contact  with  the  timer  segment 
carrying  the  insulated  wire  which  runs  to  the  coil  for  cylinder  No.  1.  The 


236 


AUTOMOTIVE  IGNITION  SYSTEMS 


gears  are  then  meshed  and  the  remaining  wires  from  the  timer  segments 
connected  to  their  respective  coils.  At  the  instant  the  roller  makes 
contact  with  the  timer  segment,  a  shower  of  sparks  begins  in  the  cylinder 
and  lasts  as  long  as  the  roller  is  on  the  segment.  Ignition,  therefore, 
occurs  when  the  timer  makes  contact  and  not  when  the  contact  is  broken, 
as  is  the  case  in  the  non- vibrating  coil  systems. 

139.  Care  and  Adjustment  of  Breakers  and  Timers. — The  breaker 
or  interrupter  is  depended  upon  to  break  the  circuit  at  the  exact  instant 
ignition  is  desired  in  the  cjdinder  of  the  engine.  In  order  that  it  may 
fulfill  this  function  properly,  the  separation  of  the  breaker  points  should 


PISTON   JUST  PAST  CENTER 


FIG.  321. — Timing  the  Ford  ignition  system. 

be  adjusted  to  that  distance  recommended  by  the  manufacturer — gen- 
erally J/50  in.  or  .020  in.  when  the  contact  arm  fiber  block  is  on  the 
highest  part  of  the  cam.  The  contact  points  should  be  dressed  off  with 
a  fine  file  or  oil-stone  to  give  a  smooth  flat  contact.  When  the  opening 
of  the  points  has  been  properly  adjusted,  the  contact  point  and  lock  nut 
should  be  set  up  tightly  to  prevent  any  possibility  of  loosening.  A 
loosened  lock  nut  will  permit  the  points  to  work  apart,  thus  throwing  the 
ignition  out  of  time.  The  tension  of  the  spring  which  brings  the  points 
together  should  be  sufficient  to  close  the  contact  with  a  firm  pressure. 
If  this  spring  tension  is  too  light,  the  points  will  not  make  good  contact 
and  the  ignition  will  be  erratic.  The  contact  arm  fiber  block  should  be 


CARE  AND  REPAIR  OF  IGNITION  APPARATUS        237 


replaced  when  it  becomes  worn.     The  contact  arm  pin  must  be  lubri- 
cated slightly  about  once  each  month  to  prevent  wear  at  this  point.     A 


CONTACT    POINTS 
TOO   FAR  APART 


CONTACT   POINTS 
PITTED  AND 
BURNED 


CONTACT   POINT 

ADJUSTING     NUT 

LOOSE 


WORN   CONTACT   ARM 
FIBRE    BLOCK 


CONTACT   ARM 
PIN   LOOSE 

CAM    LOOSE 
ON  SHAFT 


SPRING  TENSION 
TOO   LIGHT 

FIG.  322. — Conditions  causing  interrupter  trouble. 


worn  pin  should  be  replaced  with  a  new  one. 
its  shaft,  since  a  loose  cam  will  shift 
on  the  shaft  and  cause  the  ignition  to 
be  thrown  completely  out  of  time. 

The  conditions  just  mentioned  are 
shown  in  Fig.  322.  Any  improper  tim- 
ing will  generally  be  caused  by  one  or 
more  of  these  conditions.  Figure  323 
shows  the  method  of  adjusting  the  con- 
tact points  in  one  make  of  interrupter. 
A  small  wrench  to  fit  the  adjusting 
nuts  is  furnished.  This  wrench  has 
two  thickness  gages  pivoted  to  the 
handle.  One  of  the  gages  is  used  in 
setting  the  contact  points  in  the 
breaker  and  the  other  is  used  in  setting 
the  air  gap  in  the  spark  plugs. 


The  cam  must  be  tight  on 


FOR  TURNING  CONTACT 
W  AND  LOCK  NUT 


PERFECT 

ROLLER 


WORN 
ROLLER 


WEAK   SPRING 


FIG.  323. — Adjusting  interrupter  contacts. 


WORN 

ROLLER 

PIN 


^****^ 

FIG.  324. — Conditions  causing  trouble 
in  the  Ford  timer. 


Figure  324  shows  the  troubles  which  may  be  experienced  with  the 
Ford  timer.     The  timer  carries  four  contact  blocks  imbedded  in  hard 


238  AUTOMOTIVE  IGNITION  SYSTEMS 

fiber  insulation.  The  roller  on  the  timer  arm  rolls  around  this  fiber  track 
coming  into  contact  with  the  contact  blocks  in  the  proper  firing  order  of 
the  engine.  The  fiber  and  the  metal  of  the  blocks  wear  down  unevenly, 
making  a  series  of  irregularities  or  " bumps"  over  which  the  roller  must 
pass.  These  bumps  sometimes  cause  the  roller  to  jump  over  the  blocks 
without  making  contact,  especially  at  high  engine  speeds,  causing  ir- 
regular ignition.  Although  it  is  possible  to  machine  the  fiber  track  and 
metal  contact  blocks  smooth  again,  the  cost  of  this  operation  is  so  high 
that  it  is  more  economical  to  replace  that  portion  of  the  timer.  The 
roller  itself  will  wear  loose  on  its  pin  and  will  sometimes  wear  rough  on 
its  outer  surface.  When  either  of  these  conditions  is  present,  the  com- 
plete timer  arm  should  be  replaced.  The  timer  spring  must  be  strong 
enough  to  exert  considerable  pressure  between  the  roller  and  the  fiber 
track.  A  weak  spring  will  not  cause  positive  contact  between  the  roller 
and  the  contact  blocks  and  should  be  replaced  with  a  stronger  spring. 

140.  Wiring  and  Terminals. — The  units  which  compose  the  ignition 
system  should  be  carefully  connected  into  the  circuit  according  to  the 
instructions  issued  by  the  manufacturers.  This  information  can  always 
be  found  in  the  instruction  book  which  accompanies  the  automobile  when 
it  is  sold.  In  the  absence  of  a  manufacturer's  instruction  book,  the 
wiring  diagrams  given  in  this  book  may  be  used  as  they  are  based  on 
reliable  information  furnished  by  the  makers  of  the  equipment  described. 

Many  ignition  systems  use  the  single  wire  wiring  system;  that  is,  one 
side  of  the  battery  is  grounded  and  the  circuit  is  carried  from  the  other 
side  of  the  battery  to  the  switch,  the  interrupter,  and  the  coil.  The  other 
terminal  of  the  coil  being  grounded  completes  the  primary  circuit  through 
the  metal  parts  of  the  automobile  back  to  the  battery.  Instead  of 
taking  advantage  of  the  "ground"  to  carry  the  current  back  to  the  bat- 
tery, some  makers  of  ignition  equipment  use  a  second  wire,  called  the 
return  wire,  to  complete  the  primary  circuit  back  to  the  battery.  The 
secondary  circuit  is  always  grounded  at  the  coil  and  at  the  spark  plugs. 

The  wire  used  for  wiring  up  the  ignition  system  must  be  a  good  grade 
of  heavily  insulated  stranded  copper  wire  made  especially  for  this  purpose. 
The  wire  is  stranded  instead  of  being  made  of  one  large  piece  to  prevent 
breaking,  as  a  stranded  wire  will  stand  more  vibration  without  breaking 
than  a  solid  wire.  Stranded  wire  will  also  stand  more  handling  without 
injury  than  a  solid  wire.  Figure  325  shows  four  grades  of  ignition  cable, 
three  of  which  are  for  use  in  a  high-tension  circuit  and  the  fourth  in  a 
low-tension  circuit.  The  voltages  encountered  in  the  high-tension  cir- 
cuit are  sufficient  to  cause  an  electric  spark  to  jump  across  a  J^  in.  air 
gap.  For  this  reason,  the  insulation  on  high-tension  cables  must  be 
very  thick.  The  upper  cable  in  Fig.  325  is  heavily  insulated  for  severe 
high-tension  service,  such  as  might  be  encountered  on  farm  tractors 
where  the  wiring  is  exposed  to  the  weather.  In  order  that  the  rubber 


CARE  AND  REPAIR  OF  IGNITION  APPARATUS        239 

insulation  may  be  protected  from  abrasion,  the  cable  is  provided  with  a 
heavy  braided  fabric  covering.  The  second  cable  is  less  heavily  insu- 
lated, but  has  the  braided  covering  and  is  suitable  for  the  average  high- 
tension  installation.  The  third  cable  has  the  same  thickness  of  rubber 
insulation  as  the  second,  but  the  fabric  covering  has  been  left  off.  This 
cable  is  often  used  where  the  wiring  is  well  protected.  Under  such 
conditions  it  gives  good  service.  The  bottom  cable  is  lightly  insulated 
and  is  suitable  for  use  in  the  primary  circuit. 

While  the  stranded  cable  will  withstand  much  abuse  without  injury, 
it  occasionally  happens  that  the  copper  conductor  will  be  broken  within 
the  insulation.  A  break  of  this  kind  is  very  hard  to  detect,  because  the  insu- 
lation is  heavy  and  the  stranded  wire  is  relatively  light.  In  case  of  doubt 
it  is  well  to  remove  the  suspected  piece  of  cable  and  substitute  a  length 


\\\m\m>^ 


FIG.  325. — Cables  for  ignitioiTservice. 

known  to  be  perfect.     If  no  improvement  is  noted  in  the  system,  the 
suspected  piece  of  cable  may  be  returned  to  the  circuit. 

The  ends  of  the  cable  are  provided  with  terminals  as  shown  in  Fig. 
326.  These  terminals  protect  the  ends  of  the  cable  and  furnish  a  perma- 
nent fastening  at  the  binding  posts  of  the  ignition  units.  They  are 
provided  with  projecting  lips  which  are  crimped  around  the  insulation 
of  the  cable.  Smaller  projections  are  crimped  around  the  stranded  con- 
ductor itself  to  furnish  good  electrical  contact  between  the  conductor 
and  the  terminal.  Before  crimping,  the  strands  of  the  cable  are  passed 
through  the  hole  in  the  shank  of  the  terminal  and  twisted  around  and 
soldered  to  the  body  of  the  terminal.  A  common  type  of  terminal  is 
shown  in  Fig.  326^..  The  end  is  placed  over  the  binding  post  and  the  nut 
screwed  down  tight.  In  Fig.  326,  B  shows  a  terminal  having  a  forked 
end.  The  nut  on  the  binding  post  to  which  the  cable  is  to  be  attached 


240 


AUTOMOTIVE  IGNITION  SYSTEMS 


need  not  be  removed  from  the  post,  but  only  unscrewed  a  short  dis- 
tance so  that  the  terminal  can  be  slipped  under  it.  When  the  nut  is 
tightened,  the  bent  up  projections  on  the  end  of  the  terminal  keep  it  in 
place.  Figure  326  C  shows  another  type  of  terminal  with  both  open  and 
closed  ends.  It  illustrates  how  the  clips  are  bent  around  the  outside  of 
the  insulation. 


A  B  C 

FIG.  326. — Terminals  for  ignition  service. 

In  the  absence  of  a  proper  terminal,  good  service  may  be  obtained 
^by  the  method  shown  in  Fig.  327.  This  shows  the  end  of  a  cable  with 
the  insulation  cut  back  from  the  end  so  as  to  expose  about  two  inches 
of  the  stranded  conductor;  The  strands  should  be  separated  into  two 
equal  portions  as  shown  at  B.  Each  half  is  then  twisted  as  in  C,  and 
the  two  parts  bent  to  form  a  circle  large  enough  to  slip  over  the  bind- 


OLD    TERMINAL 


BCD 

FIG.  327. — Method  of  making  temporary 
terminals. 


FIG.  328.- 


-Method  of  using  old  terminals 
on  new  wires. 


ing  post  easily    as    in    D.     The    strands  are  then  soldered   together. 
This  makes  a  stiff  firm  ending  which  will  last  some  time. 

In  replacing  cables,  when  no  new  terminals  are  at  hand,  the  old 
terminal  may  be  made  to  serve  as  shown  in  Fig.  328.  The  old  termi- 
nal is  cut  off  of  the  old  cable,  leaving  about  two  inches  of  the  conductor 
attached.  The  insulation  is  removed  from  the  new  wire  for  two  inches 


CARE  AND  REPAIR  OF  IGNITION  APPARATUS'      241 

and  the  two  wires  twisted  together.     After  the  joint  has   been  well 
wrapped  with  friction  tape,  the  terminal  is  ready  for  service. 

When  making  connections  in  wiring  of  this  nature,  it  is  of  the  ut- 
most importance  that  good  electrical  contact  be  secured  between  the 
two  parts  which  are  joined.  For  this  reason,  the  parts  should  be  care- 
fully cleaned  and  scraped  to  insure  close  metallic  contact.  They  should 
then  be  soldered  together.  The  smallest  quantity  of  solder  consistent 
with  good  workmanship  should  be  used.  The  process  most  often  em- 
ployed is  known  as  " sweating"  the  parts  together.  This  is  accom- 
plished by  applying  the  soldering  flux  to  the  parts  after  they  have  been 
scraped  bright  and  then  dipping  them  into  a  pot  of  melted  solder. 
A  film  of  solder  will  immediately  attach  itself  to  the  parts.  This  process 
is  called  "tinning."  If  the  two  parts  which  are  to  be  united  are  then 
twisted  or  held  together  and  placed  in  the  flame  of  a  blow  torch  until 


FIG.  329. — Flexible  conduits  for  electric  wiring. 

the  film  of  solder  is  melted  and  then  allowed  to  cool  without  disturbance, 
a  perfect  joint  will  result. 

The  wiring  on  automobiles  is  often  protected  from  mechanical  in- 
jury by  enclosing  it  in  metallic  or  fabric  tubing  called  "conduit." 
Figure  329  shows  two  kinds  of  conduit  in  common  use  ior  this  purpose. 
The  upper  figure  shows  a  section  of  flexible  metal  tubing  made  of  me-' 
tallic  strips  wound  spirally  around  a  mandrel.  The  strips  are  so  inter- 
linked that  after  the  mandrel  is  removed  there  remains  a  continuous 
flexible  metal  tubing  that  may  be  bent  easily  around  short  corners. 
This  is  excellent  for  protecting  the  electrical  conductors  from  injury. 
The  lower  figure  shows  a  section  of  "circular  loom"  made  up  of  two 
layers  of  heavy  cotton  tubing  impregnated  with  a  frictioning  material. 
This  forms  an  effective  and  low-priced  protection  for  the  wiring. 

141.  Wiring  the  High-tension  System. — The  wire  used  in  the  high- 
tension  system  may  be  of  any  of  the  three  grades  shown  in  the  upper 
part  of  Fig.  325.  These  cables  afford  ample  insulation  for  the  high 
secondary  voltages.  They  should  be  provided  at  the  spark  plug  ends 
with  good  copper  terminals  similar  to  those  shown  in  Fig.  326.  The 

16 


242 


AUTOMOTIVE  IGNITION  SYSTEMS 


distributor  ends  are  usually  gripped  in  the  terminals  on  the  distributor 
unit  and  require  no  special  preparation.  The  high-tension  cables  are 
well  protected  from  mechanical  injury  by  being  enclosed  in  metal  conduit 
for  the  greater  portion  of  their  length.  This  protection  is  necessary 
because  of  the  fact  that  any  injury  to  the  insulation  on  the  cable  would 
permit  the  high-tension  current  to  escape  at  the  point  of  injury  and  thus 
cause  a  missing  cylinder  on  the  engine.  Oil  is  very  detrimental  to  the 
rubber  insulation,  causing  it  to  soften  and  lose  its  insulating  properties. 
For  this  reason,  the  wiring  of  the  ignition  system  should  be  protected 
from  oil.  Any  oil  inadvertently  spilled  on  the  wiring  should  be  wiped 
off  immediately. 

142.  Testing  High-tension  Insulation. — A  high-tension  cable  which 
is  suspected  of  having  weak  insulation  may  be  tested  by  the  method 
shown  in  Fig.  330.  A  single  vibrating  coil  is  connected  to  a  suitable 
battery.  The  cable  under  test  is  connected  to  one  of  the  secondary 
terminals  on  the  coil.  A  metal  ring  just  large  enough  to  encircle  the 


HIGH  TENSION  CABLE 


TO  BATTERY 


FIG.  330. —  Testing  the  insulation  of  high-tension  cables. 

cable  snugly  is  fitted  in  one  end  of  an  insulating  handle.  A  wire  run- 
ning through  the  handle  makes  contact  with  the  ring  and  with  the  other 
secondary  terminal  on  the  coil.  When  the  primary  circuit  is  closed, 
the  vibrating  coil  will  impress  a  series  of  high-tension  current  surges 
upon  the  cable.  With  the  coil  in  action,  the  ring  is  moved  slowly  along: 
the  cable.  Any  weak  spot  in  the  insulation  of  the  suspected  cable 
will  permit  a  spark  to  jump  from  the  ring  through  the  punctured  insula- 
tion to  the  conductor  at  the  center  of  the  cable.  This  spark  causes 
a  series  of  sharp  snappy  sounds.  If  no  such  sounds  are  heard,  the 
cable  may  be  safely  used. 

143.  Care  of  the  Distributor. — The  distributor  handles  the  high- 
tension  current  generated  in  the  secondary  winding  of  the  coil.  Its 
function  is  to  receive  this  high-tension  current  from  the  coil  and  direct 
it  to  the  proper  spark  plugs  in  the  regular  firing  order  of  the  engine.  In 
some  units,  this  distribution  is  accomplished  by  a  rotating  arm  carrying 
a  carbon  brush.  This  carbon  brush  presses  on  the  vulcanized  rubber 


CARE  AND  REPAIR  OF  IGNITION  APPARATUS        243 

cap  of  the  distributor,  as  the  arm  rotates,  and  makes  contact  with  the 
distributor  segments.  The  friction  between  the  brush  and  its  track 
causes  a  certain  amount  of  carbon  to  wear  off  as  dust.  If  this  dust  is 
allowed  to  collect,  it  will  interfere  with  the  proper  operation  of  the  dis- 
tributor by  causing  short  circuits  from  one  segment  to  another.  For 
this  reason,  the  distributor  cap  should  be  wiped  out  occasionally  to  re- 
move this  dust.  Oil  in  large  quantities  is  a  detriment  in  the  distributor 
because  it  holds  the  carbon  dust,  thus  aggravating  the  trouble.  How- 
ever, a  very  slight  amount  of  vaseline  applied  to  the  distributor  brush 
track  will  lessen  the  friction  and  reduce  .the  quantity  of  carbon  dust. 
The  track  should  be  rubbed  over  with  a  rag  dampened  with  vaseline, 
and  then  wiped  with  a  dry  cloth.  The  imperceptible  film  of  oil  left  by 
this  process  is  enough  to  provide  the  proper  amount  of  lubrication  without 
retaining  the  dust  worn  from  the  brush. 

In  another  form  of  distributor  the  rotating  arm  does  not  make  actual 
contact  with  the  distributor  segments,  but  the  arm  ends  in  a  metallic 
segment  which  passes  very  close  to,  but  does  not  touch,  the  segment 
attached  to  the  spark  plug  leads.  The  surge  of  high-tension  current  is 
forced  to  jump  the  short  air  gap  between  the  two  parts.  After  consider- 
able service,  this  arc  will  have  partly  burned  away  the  metal  parts  at 
the  gap,  causing  the  gap  to  widen.  New  segments  should  be  applied 
before  the  gap  becomes  so  wide  that  the  spark  will  no  longer  jump 
across. 

Moisture  will  interfere  with  the  operation  of  a  distributor;  therefore, 
it  is  advisable  to  keep  water  away  from  this  unit.  In  washing  the  car, 
water  is  sometimes  splashed  through  the  radiator  and  hood  upon  the 
electrical  equipment.  This  should  be  carefully  wiped  away  before  at- 
tempting to  start  the  engine. 

144.  Installation  and  Care  of  Spark  Plugs. — The  spark  plugs  should 
be  carefully  screwed  in  place  in  the  cylinder.  Just  sufficient  e-ort 
should  be  used  on  the  wrench  to  set  them  firm  enough  to  prevent  leakage. 
If  any  additional  pressure  is  used,  it  will  be  difficult  to  remove  the  plug 
and  damage  may  possibly  result.  The  %-in.  plug  uses  a  copper-asbestos 
gasket  to  provide  an  air-tight  fit  between  the  plug  and  the  cylinder.  This 
gasket  should  be  renewed  when  it  becomes  much  flattened.  With  a 
J^-in.  plug  the  tightening  of  the  joint  depends  upon  the  taper  of  the 
standard  pipe  thread  used. 

The  combustion  of  the  fuel  mixture  in  the  presence  of  lubricating  oil 
in  the  cylinders  of  the  engine  leaves  a  deposit  of  carbon  on  the  plug. 
This  carbon  will  often  render  the  plug  inactive  by  providing  a  short 
circuit  between  the  firing  points.  It  may  be  removed  from  the  plug  by 
scraping  with  a  penknife  or  a  wire  brush.  Gasoline  is  also  useful  for 
this  purpose. 

The  points  of  the  plug  should  be  adjusted  to  give  a  spark  gap  of 


244  AUTOMOTIVE  IGNITION  SYSTEMS 

about  .030  in.  A  thickness  gage  gives  a  ready  means  of  making  this 
adjustment  correctly.  In  the  absence  of  such  a  gage,  a  thin  dime  may 
be  used  as  an  approximation.  A  wider  setting  than  this  distance  will 
cause  the  engine  to  miss  at  slow  speeds  under  heavy  load,  due  to  the  pos- 
sibility of  the  spark's  not  jumping  the  wide  gap  through  the  highly  com- 
pressed gas.  This  action  is  especially  noticeable  on  magneto  ignition 
as  the  spark  produced  by  the  magneto  at  low  speed  is  liable  to  be  weak. 
If  the  gap  is  extremely  narrow,  the  engine  may  miss  when  running  slowly 
under  a  light  load  as  the  length  of  spark  may  not  be  sufficient  to  gen- 
•erate  heat  enough  to  ignite  the  thin  mixture  then  present  in  the  cylinder. 
The  variations  of  heat  to  which  the  porcelain  insulator  is  subjected 
sometimes  causes  it  to  crack.  A  cracked  porcelain  should  be  replaced 
since  the  current  will  follow  the  path  of  least  resistance  through  the  crack 
rather  than  jump  the  gap  between  the  points  in  the  highly  compressed 
charge  in  the  cylinder. 

145.  Spark  Plug  Testing. — The  porcelain  of  a  spark  plug  may  become 

cracked,  due  to  the  intense  heat  of  the 
engine  or  to  an  accident.  The  plug 
is  then  usually  short  circuited  through 
the  crack  in  the  porcelain;  conse- 
quently, no  spark  is  produced  in  the 
cylinder.  A  broken  porcelain  may 
sometimes  be  detected  by  a  grating 
sound  when  an  effort  is  made  to 
wiggle  the  porcelain  of  the  plug  with 
the  fingers  before  the  plug  is  removed 
from  the  cylinder.  The  plug  may 

FIG.  331.-Method  of  locating  a  misfir-     als°  beCOme    sh°rt    circuited    through 

ing  cylinder.  carbon   Or  oil  deposits   between  the 

plug  points. 

The  spark  plug  which  seems  to  spark  properly,  when  tried  out  on  the 
cylinder  block  in  the  open  ,  air,  may  fail  entirely  inside  the  cylinder 
because  of 'the  increased  resistance  offered  to  the  passage  of  the  spark 
across  the  gap  under  the  high  compression  in  the  cylinder.  For  this 
reason,  the  most  satisfactory  way  to  test  a  plug  is  to  test  it  under  actual 
operating  conditions.  To  determine  which  cylinder  is  missing  fire,  the 
plugs  may  be  short  circuited,  one  or  more  at  a  time,  with  the  engine 
running,  by  holding  a  screwdriver  or  hammer  head  from  the  plug  ter- 
minal to  the  cylinder  head,  as  shown  in  Fig.  331,  or  the  wires  may  be 
removed  from  the  spark  plug,  one  or  more  at  a  time,  and  the  change  in 
the  engine  power  noted.  If  the  plug  under  test  has  not  been  operating, 
there  will  be  no  change  in  the  engine  power,  but  if  the  engine  shows  a 
material  loss  of  power,  it  may  be  safely  concluded  that  the  plug  has 
been  operating  satisfactorily,  The  priming  cups  may  be  opened  one  at 


CARE  AND  REPAIR  OF  IGNITION  APPARATUS        245 


a  time  and  the  issuing  flame  watched.     A  hot  flame  should  issue  with 
each  explosion  of  the  cylinder. 

A  sooty,  oily  appearance  of  the  spark  plug  points,  when  removed 
from  the  cylinder,  also  indicates  that  the  plug  has  not  been  working 
properly.  A  white,  or  yellowish  white,  clean,  dry  appearance  of  the 
porcelain  indicates  that  the  cylinder  has  been  firing.  Probably  the 
most  satisfactory  method  of  testing  a  spark  plug  is  to  exchange  plugs 


SPARK 


AMMETER 


FIG.  332. — Champion  spark  plug  cleaner. 

between  the  cylinders  or  to  try  out  a  plug  which  is  known  to  be  good,  in 
the  cylinder  which  is  misfiring. 

If  the  plug  is  not  to  be  taken  apart,  it  can  be  cleaned  with  a  brush 
and  gasoline.  If  it  is  taken  apart,  the  porcelain  may  be  cleaned  without 
scratching  by  using  water  and  a  little  road  dust.  Emery  cloth  should 
not  be  used  as  it  will  scratch  the  porcelain.  Figure  332  shows  the  Cham- 
pion spark  plug  cleaner  which  screws  onto  the  plug.  The  container  is 
filled  with  gasoline  and  upon  being  shaken,  the  needles,  in  combination 
with  the  gasoline,  remove  any  carbon 
deposit  that  may  be  on  the  plug. 

146.  Ignition  Coil  Testing.— The 
ignition  coil  can  be  examined  only 
from  the  outside.  Most  manufac- 
turers seal  the  coil  by  impregnating 
the  windings,  etc.  with  a  hard  wax  or 
pitch  composition.  This  holds  the 
parts  in  the  proper  place  and  also 
provides  the  thorough  insulation 
which  the  coil  requires.  The  condi- 
tion of  the  different  parts  of  the  coil 
can  be  determined  by  tests  made  from  the  outside  of  the  coil. 

Vibrating  Coils. — Vibrating  ignition  coils  may  be  tested  by  the  method 
shown  in  Fig.  333.  A  special  low  reading  ammeter  whose  scale  is  gradu- 
ated from  0  to  3  amperes  is  connected  in  series  with  the  primary  winding 
and  vibrator  of  the  coil  and  a  6-volt  battery,  either  storage  or  dry  cells. 
Leads  which  terminate  in  a  Ji-m.  spark  gap  are  provided  from  the  second- 
ary terminals  of  the  coil.  When  the  circuit  is  completed  through  the 
primary  winding,  the  vibrator  should  vibrate  freely,  giving  off  a  continu- 
ous and  rather  high-pitched  tone.  The  current  flow,  as  indicated  by  the 


BATTERY 

FIG.  333. — Testing  vibrating  ignition  coil. 


246  AUTOMOTIVE  IGNITION  SYSTEMS 

ammeter,  may  be  regulated  by  adjusting  the  vibrator  to  from  %  to  1J^ 
amperes.  There  should  then  be  a  continuous  flow  of  heavy  blue  sparks 
at  the  spark  gap.  Thin,  yellow  sparks  indicate  a  poorly  adjusted  or 
weak  coil.  The  adjustment  should  be  varied  until  the  spark  has  con- 
siderable volume.  When  the  spark  is  blown  upon/  it  should  spread  and 
bend  away  from  the  points  in  the  direction  of  the  air  current.  If  it 
breaks  and  becomes  irregular,  the  vibrator  is  not  properly  adjusted. 

If  the  vibrator  operates  properly  and  there  is  no  spark  at  the  spark 
gap,  the  secondary  circuit  is  probably  open  inside  the  coil.  Poor  insu- 
lation will  permit  the  secondary  current  to  jump  across  the  defective 
insulation  within  the  coil  instead  of  making  its  appearance  at  the  spark 
gap.  This  condition  is  frequently  indicated  by  a  buzzing  noise  accom- 
panied by  smoke  issuing  from  the  interior  of  the  coil,  and  can  be  remedied 
only  at  an  electrical  service  station.  The  coil  is  usually  returned  to 
the  maker  for  repair. 

An  excessive  reading  of  the  ammeter  indicates  a  short  circuit  in  the 
primary  winding,  or  that  the  vibrator  points  are  stuck  together.  If, 
after  examining  the  points  and  dressing  them  smooth,  the  high  reading 
continues,  it  may  be  safely  assumed  that  the  primary  winding  is  at 
fault.  The  coil  should  then  be  sent  to  the  manufacturer  for  correction. 
A  poor  connection  will  cause  the  ammeter  needle  to  jump  about  instead 
of  remaining  steady. 

When  the  coil  is  operating  properly,  a  faint  yellow  spark  will  appear 
at  the  vibrator  points.  Should  this  spark  become  blue  in  color  and  larger 
in  volume,  emitting  a  snappy  sound,  the  condenser  within  the  coil  is 
probably  not  functioning,  either  because  the  insulation  between  the 
leaves  of  the  condenser  has  been  punctured  and  the  condenser  short 
circuited  or  because  the  condenser  circuit  is  open.  The  result  will  be 
evidenced  in  rapidly  pitting  vibrator  points,  requiring  their  renewal  at 
frequent  intervals.  A  defective  condenser  must  be  replaced  by  the  maker 
of  the  coil. 

A  light  tension  on  the  vibrator  spring  means  economy  of  current, 
but  if  the  tension  is  too  light  the  engine  will  not  run  evenly.  On  the 
other  hand,  a  heavy  tension  on  the  vibrator  points  means  an  excessive 
current  consumption  by  the  coil,  resulting  in  pitting  of  the  points  due  to 
the  incapacity  of  the  condenser  to  absorb  the  increased  amount  of  energy 
stored  in  the  magnetic  field. 

Non-vibrating  Coils. — Non-vibrating  coils  are  very  simple  in  their 
make-up,  containing  only  a  magnetic  core  and  primary  and  secondary 
windings.  On  some  coils  the  condenser  and  the  safety  spark  gap  are 
also  included  in  the  assembly,  but  often  either  one  or  both  of  these  are 
contained  in  other  parts  of  the  ignition  system. 

A  test  of  the  proper  working  of  the  coil  may  be  made  by  attaching  one 
end  of  a  piece  of  wire  to  the  metal  part  of  the  engine  and  by  bringing  the 


CARE  AND  REPAIR  OF  IGNITION  APPARATUS        247 

other  end  to  within  J^  in.  of  the  secondary  terminal  of  the  coil.  The 
breaker  points  in  the  interrupter  are  then  opened  and  closed.  If  a  good 
snappy  spark  jumps  the  gap  from  the  secondary  terminal  to  the  end  of 
the  grounded  wire  every  time  the  points  are  separated,  the  coil  is  in 
perfect  condition  and  whatever  trouble  is  present  may  be  looked  for  in 
the  other  parts  of  the  ignition  system.  A  failure  of  the  spark  to  appear 
may  be  the  result  of  any  one  of  the  conditions  mentioned  in  the  following 
paragraphs. 

Moisture  in  the  safety  spark  gap  may  lower  its  resistance  so  that  the 
spark  will  occur  at  this  point.  The  safety  spark  gap  should  be  dried 
carefully  to  eliminate  all  traces  of  moisture. 

A  defective  condenser  will  not  absorb  the  hang-over  current  produced 
by  the  self-induction  of  the  primary  winding.  This  will  prolong  the 
collapse  of  the  magnetic  field  to  such  an  extent  that  the  required  voltage 
will  not  be  built  up  in  the  secondary  winding.  Excessive  sparking  at 
the  interrupter,  points  to  this  condition.  If  the  condenser  is  mounted  so 
that  it  can  be  removed,  as  in  the  case  of  the  Atwater-Kent  closed 
circuit  system,  it  may  be  taken  out  and  tested  by  the  method  described 
in  Section  147.  If  the  condenser  is  contained  within  the  coil,  the  entire 
unit  must  be  returned  to  the  manufacturer. 

147.  Condenser  Troubles  and  Method  of  Testing. — The  condenser  i 
is  connected  in  parallel  with  the  vibrator  points  in  vibrating  coil  ignition 
systems  and  in  parallel  with  the  breaker  points  in  non-vibrating  coil 
systems.  Its  purpose  is  to  absorb  the  after-current  generated  by  the 
self-inductive  action  of  the  primary  winding  and  to  prevent  this  current 
from  making  its  appearance  at  the  contact  points  in  the  form  of  an  arc 
or  spark.  The  absorption  of  this  current  also  causes  a  quicker  collapse 
of  the  magnetic  field,  causing  the  secondary  to  build  up  a  current  surge 
of  a  much  higher  voltage  than  when  the  condenser  is  not  present  or  is  not 
working  properly.  The  proper  action  of  the  condenser  has  an  important 
effect  on  the  quality  of  the  spark  produced.  An  ignition  system  that  will 
give  a  hot  fat  spark  with  the  condenser  operating  properly  will  give  but 
a  feeble  spark  when  the  condenser  is  removed  or  is  in  poor  condition. 

The  troubles  liable  to  be  found  in  a  condenser  are  two  in  number. 
The  insulation  between  the  tinfoil  layers  in  the  condenser  may  be  punc- 
tured, allowing  the  two  sides  to  make  electrical  contact  with  each  other, 
in  which  case  the  condenser  is  said  to  be  shorted;  or  the  connections  to  the 
condenser  may  be  broken. 

In  the  first  case,  the  current  will  flow  through  the  condenser  without 
hindrance.  The  primary  current  will  not  be  interrupted,  when  the 
contact  points  are  opened,  and  no  spark  will  be  produced  in  the  cylinder. 
In  the  second  case,  the  condenser  is  not  permitted  to  absorb  the  self- 
induced  current  in  the  primary  circuit  and  a  weak  spark  is  produced  in 
the  cylinder. 


248 


AUTOMOTIVE  IGNITION  SYSTEMS 


CONDENSER 


The  probable  condition  of  the  condenser  is  determined  by  a  simple 
test  made  as  follows:  The  interrupter  points  are  opened  and  closed  and 
the  quality  of  the  spark  produced  at  a  gap  of  about  J4  in.  in  the  secondary 
circuit  noted.  If  the  spark  is  vigorous  and  there  is  not  excessive  sparking 
at  the  contact  points,  when  they  are  opened,  the  condenser  is  functioning 
properly.  If  there  is  considerable  spark  at  the  contact  points  and  the 
spark  produced  at  the  gap  is  feeble,  there  is  probably  a  loose  connection 
or  an  open  circuit  in  the  condenser  circuit.  If  no  spark  is  produced  at 
the  gap  and  no  spark  occurs  at  the  contact  points,  upon  separation, 
while  at  the  same  time  the  ammeter  shows  the  usual  current  to  be  flowing, 
the  insulation  in  the  condenser  has  been  destroyed  or  the  condenser 
shorted  in  some  manner. 

If  the  condenser  is  placed  in  such  a  position  that  it  can  be  removed 
from  the  other  parts  of  the  ignition  system,  it  can  be  tested  in  the  man- 
ner shown  in  Fig.  334.  A  110-volt  direct-current  service  is  used.  A 

60-watt  lamp  is  connected,  as  shown  in 
the  diagram,  in  series  with  the  con- 
denser, and  the  two  contact  points  A 
are  so  arranged  that  when  they  are 
A  brought  together  the  condenser  is  short 
circuited.  With  the  contacts  points  A 
separated  and  the  switch  closed,  the 
lamp  will  be  dark  if  the  condenser  is  in 
good  condition.  Upon  bringing  the 
for  testing  points  A  together,  a  snappy  spark  will 
occur  at  this  point  and  the  lamp  will 
light  up  as  long  as  the  points  are  in  contact.  When  the  points  are 
again  separated,  the  lamp  will  go  out.  When  the  switch  is  opened 
and  the  contacts  brought  together,  a  heavy  spark  will  result  from  the 
charge  stored  in  the  condenser.  If  the  lamp  burns  with  the  switch 
closed  and  the  points  A  apart,  the  condenser  is  shorted  because  of  de- 
fective insulation.  If  the  lamp  remains  dark  under  these  conditions 
and  still  no  spark  is  given  at  the  points  when  they  are  brought  together 
after  the  switch  has  been  opened,  the  condenser  is  in  open  circuit — 
there  is  a  poor  connection  or  a  break  in  the  wires  leading  to  the  condenser. 
Defective  condensers  are  not  easily  repaired  on  account  of  their 
delicate  construction  and  also  because  of  the  fact  that  they  are  often 
sealed  within  the  coils.  The  most  economical  method  of  curing  a 
defective  condenser  is  to  send  it  back  to  the  maker  for  replacement. 

A  condenser  sealed  within  the  spark  coil  of  a  battery  ignition  sys- 
tem, or  contained  in  the  armature  of  a  magneto,  is  often  difficult  to 
test  because  of  the  fact  that  it  is  often  paralleled  by  other  parts  of  the 
circuit.  By  examining  the  wiring  diagram,  .it  is  possible  to  determine 
whether  the  condenser  can  be  isolated  between  two  terminals  of  the 


FIG. 


LAMP 

334.  —  Connections 
condenser. 


CARE  AND  REPAIR  OF  IGNITION  APPARATUS        249 


ISTANCE 
COIL 


coil.  If  so,  the  test  outlined  can  be  made.  In  Fig.  335  is  shown  the 
Remy  two  primary  .terminal  coil  with  the  terminals  between  which 
the  condenser  is  located.  All  that  is  neces- 
sary is  to  connect  these  two  terminals  into 
the  circuit  shown  in  Fig.  334  at  the  points  C 
and  D.  Figure  336  shows  the  two  terminals 
used  for  testing  the  condenser  in  the  Delco 
coil,  and  Fig.  337  shows  the  two  terminals  used 
for  testing  the  condenser  in  the  Connecticut 
coil.  In  each  of  these  cases  it  will  be  noted 
that  the  condenser  is  the  only  part  of  the  coil 
included  between  the  terminals  indicated. 

148.  Recharging  Magnets. — The  magnets 
used  on  magnetos  to  provide  the  magnetic 
field  are  called  permanent  in  the  sense  that 
they  will  retain  their  magnetism  for  a  con- 
siderable length  of  time.     They  will,  however, 
gradually  lose  their  magnetic  strength,  and 
after  an  extended  period  of  use  will  have  to 
be  recharged.     This  is  especially  true  if  the 
magneto  has  been  subjected  to  rough  handling,  or  if  the  magnets  have 
been  removed  from  the  magneto  and  subjected  to  jars  and  mechanical 
shocks  while  separated  from  the  rest  Tpc.T  rOM 
of  the  magneto.  BETWEEN  CENTER 


FIG.  335. — Condenser  con- 
nections in  Remy  two- terminal 
coil.  Test  condenser  between 
Int.  terminal  and  base  of  coil. 


A  fully  charged  magnet,  such  as  TERMINAL  AND 
is  used  on  magnetos,  should  be  able  C)ROUND>\ 
to  lift  a  piece  of  steel  weighing  from 
12  Ib.  to  14  Ib.     If  the  spark  produced 
by  the   magneto   is   weak   and  it  is 


SAFETY  GAP 


RE5I5TANCENUNIT 
D!ST."D'j 

si 


CONDFN5ER- 


—  GR"C" 


XONDEN5ER 


FIG.  336. — Condenser  connections  in  Delco 
coil.^Test  condenser  between  Dist.  terminal 
and  base  of  coil. 


FIG.    337. — Condenser    connections   in 
Connecticut  coil. 


suspected  that  the  magnets  have  lost  their  strength,  they  should  be  re- 
moved from  the  instrument  and  tested.     If  they  will  not  lift  the  required 


250 


AUTOMOTIVE  IGNITION  SYSTEMS 


weight,  they  should  be  recharged.     After  a  magnet  has  been  removed 
from  a  magneto,  it  should  be  handled  as  little  as  possible.     A  piece  of 

soft  iron  or  steel,  called  a  keeper,  should  be 
placed  across  the  ends  as  shown  in  Fig.  338. 
This  keeper  provides  a  path  for  the  magnetic 
lines  of  force  of  the  magnet  and  helps  to  con- 
serve its  strength.  It  should  be  in  place  at 
all  times  except  when  other  operations  neces- 
sitate its  removal. 

The  poles  of  the  magnets  are  sometimes 
marked  N  and  S  to  distinguish  the  north  and 
south  poles,  respectively.  The  magnetic  lines 
of  force  leave  the  magnet  by  the  North  pole 

FIG.  338.— Magnet^with  keeper     and   enter   by  the   South   pole.      The  polarity 

of  the  magnet  can  be  determined,  if  the  poles 

are  not  marked,  or  the  marking  checked,  by  the  method  shown  in  Fig. 
339.     A  small  pocket  compass  is  brought  near  the  poles  of  the  magnet; 

the  end  of  the  compass  needle  that  points 
to  the  north  will  point  to  the  South 
pole  of  the  magnet,  and  vice  versa.  It 
is  well  to  check  the  marking  on  the  mag- 


FIG.  339. — Determining  polarity  of  a 
magnet. 


FIG.  340. — Magnet  recharger. 


net,  if  there  is  any,  to  see  if  the  magnetism  has  been  reversed  by  a  pre- 
vious recharging. 

To  recharge  a  magnet  it  is  only  necessary  to  bring  it  into  a  strong 


CARE  AND  REPAIR  OF  IGNITION  APPARATUS        251 


magnetic  field  for  a  short  time.  This  field  is  usually  provided  by  a 
large  electromagnet  similar  to  the  one  shown  in  Fig.  340.  This  shows  the 
electromagnet  connected  to  a  source  of  current  of  the  proper  voltage. 
Most  electromagnets  of  this  nature  are  wound  for  use  on  a  110-volt 
circuit,  and  are  connected  directly  to  a  direct-current  line.  The  electro- 
magnet has  two  poles.  Its  polarity  can  be  determined  by  testing 
with  a  pocket  compass.  When  this  has  been  determined,  its  poles  should 
be  marked  with  pencil  or  chalk.  The  magnet  to  be  charged  should  then 
be  placed  on  the  electromagnet  with  its  North  pole  on  the  South  pole 
of  the  electromagnet,  and  its  South  pole  on  the  North  pole  as  shown 
in  Fig.  340.  Current  should  then  be  turned  into  the  windings  of  the  elec- 
tromagnet for  a  few  seconds,  meanwhile  rocking  the  magnet  back  and 
forth  on  the  electromagnet  or  jarring  the  magnet  by  several  light  blows 
from  a  mallet.  The  object  of  the  rocking  and  the  blows  is  to  enable 
the  molecules  of  the  magnet  to 
arrange  themselves  so  as  to  give  the 
greatest  magnetic  strength.  A  very 
short  time  is  required  to  remagnetize 
the  magnet.  The  current  should 
be  turned  off  in  about  J£  minute. 
The  magnet  should  be  removed 
from  the  electromagnet  and  its  lift- 
ing power  tested.  If  satisfactory, 
the  keeper  should  be  placed  on  the 
poles  of  the  magnet  and  the  mag- 
net returned  to  the  magneto  as 
quickly  as  possible.  Care  should 
be  taken  to  charge  all  magnets  of 
a  set  to  the  same  strength.  They 
also  should  be  of  the  same  quality  of  steel. 

Figure  341  shows  the  Aero  magneto  with  a  keeper  placed  across  the 
poles  of  the  magnet.  This  keeper  should  be  placed  in  position  while 
the  magnet  is  still  in  the  magneto.  The  makers  of  this  instrument 
recommend  this  practice  in  order  to  protect  the  magnet  as  much  as 
possible.  Figure  342  shows  the  magnet  recharger  furnished  by  the  manu- 
facturers of  this  magneto  to  their  service  stations  for  recharging  the 
magnets  of  their  magnetos.  A  master  magnet  is  kept  in  the  coils  of 
this  recharger  at  all  times.  The  magnet  to  be  recharged  is  attached 
to  the  master  magnet  and  is  then  pushed  forward  so  that  it  is  within 
'the  coils.  The  switch  is  then  closed,  permitting  the  current  to  flow  for 
a  few  seconds.  It  is  then  opened  and  the  magnet  pulled  forward  and 
the  keeper  placed  across  the  ends  of  the  magnet.  The  magnet  is  then 
removed  from  the  recharger  and  placed  in  position  on  the  magneto  with 
the  keeper  still  in  place.  When  the  magnet  is  again  in  place  in  the 
magneto,  the  keeper  is  lifted  off. 


FIG.     341. — Keeper     on     magnet    in    Aero 
magneto. 


252 


AUTOMOTIVE  IGNITION  SYSTEMS 


Apparatus  for  recharging  magnets  need  not  be  so  complete  or  so 
elaborate  as  the  methods  just  described.  The  magnet  may  be  recharged 
by  the  method  shown  in  Fig.  343  from  a  110- volt  D.  C.  line.  The 
polarity  of  the  magnet  is  first  determined  with  the  aid  of  a  small 
compass,  while  the  polarity  of  the  line  is  determined  by  the  method  de- 


110  VOLT 

D.C.LINE 


FIG.  342. — Recharger  for  Aero  magneto. 

scribed  in  Chapter  I.  A  lamp  bank  containing  thirty  32-candlepower 
carbon  filament  incandescent  lamps  is  connected  to  one  side  of  the  line 
and  a  length  of  insulated  wire  similar  to  that  used  in  No.  16  lamp  cord 
is  wrapped  around  the  legs  of  the  magnet  until  no  more  can  be  added. 
The  direction  of  winding  the  wire  on  the  magnet  must  be  given  special 

attention.  The  magnet  is  taken  in 
the  right  hand  with  the  thumb  ex- 
tending in  the  direction  of  the  lines 
of  force  from  the  magnet  (out  of  the 
North  pole  and  in  at  the  South  pole). 
The  wire  should  be  wound  around 
the  magnet  so  that  the  current  will 
flow  through  the  winding  and  around 
the  magnet  in  the  direction  in  which 
the  fingers  encircle  it.  These  direc- 
tions have  been  carried  out  in  Fig. 
343.  A  careful  study  of  this  illustra- 
tion will  make  the  method  clear.  The 
current  is  permitted  to  flow  for  a  few 
seconds  and  the  magnet  is  then 
recharged. 

Recharging  the  Magnets  on  the  Ford  Magneto. — The  magnets  on  the 
Ford  magneto  may  be  recharged  in  the  manner  just  described,  but  their 
removal  is  so  difficult  that  they  are  usually  recharged  in  place  on  the 
flywheel.  The  method  sometimes  adopted  for  this  purpose  is  shown  in 
Fig.  344.  Before  this  method  is  used,  the  magneto  must  be  carefully 


FIG.  343. — Simple  method  of  recharging 
magnet. 


CARE  AND  REPAIR  OF  IGNITION  APPARATUS        253 


placed  in  the  proper  position.  This  is  done  by  holding  a  small  compass 
1  in.  to  the  left  and  6  in.  to  the  rear  of  the  magneto  terminal.  The  engine 
is  then  slowly  cranked  until  the  needle  on  the  compass  points  straight  to- 


CHEHO 
OF  Wl*C  TO  FRAMC 


FIG.  344. — Recharging  magnets  of  Ford  magneto. 

ward  the  front  of  the  car  as  shown  in  Fig.  345.     Five  6-volt  storage^bat- 
teries  connected  in  series  are  used  as  a  source  of  current.     The  positive 


V^f 

PLAN    VIEW 


COMP, 


FIG.  345. — Setting  Ford  magneto  for  recharging  magnets. 

terminal  of  the  set  is  connected  to  the  magneto  terminal  after  disconnect- 
ing the  lead  running  to  the  ignition  and  lighting  systems.  The  other 
end  of  the  set  of  batteries  has  a  lead  attached  with  which  the  frame  or 


254  AUTOMOTIVE  IGNITION  SYSTEMS 

metal  work  of  the  car  is  touched  two  or  three  times  for  about  a  second 
at  a  time.  The  arc  which  forms,  when  the  connection  is  broken,  should 
be  pulled  out  slowly.  The  coils  of  the  magneto  act  in  the  same  way  as 
the  windings  of  an  electromagnet  and  build  up  the  strength  of  the  mag- 
nets. With  this  arrangement  about  48  amperes  of  current  are  permitted 
to  pass  through  the  magneto  coils  on  the  older  Ford  models  and  about 
56  amperes  on  the  later  models.  The  results  produced  by  this  method 
.are  often  not  satisfactory  and  the  method  should  not  be  used  except  by 
one  familiar  with  the  handling  of  electrical  equipment. 

A  satisfactory  method  of  charging  the  Ford  magnets  while  still  in  the 
car  is  to  use  a  special  magnetizer  made  for  this  purpose  which  can  be 
applied  to  the  magnets  through  the  opening  for  the  gear  case  cover. 
This  magnetizer  can  be  had  to  operate  on  current  from  a  six- volt  storage 
battery  or  from  110  volt  D.  C.  lines. 


CHAPTER  X 
IGNITION  TROUBLES  AND  REMEDIES 

149.  Starting  the  Engine. — The  modern  automobile  engine  is  set  in 
motion  by  an  electric  starting  motor.     This  motor  takes  the  place  of  the 
old  method  of  cranking  the  engine  by  hand  and  thus  removes  one  of  the 
inconveniences  of  the  early  day  automobile.     Before  the  engine  is  started, 
the  ignition  switch  is  turned  "ON,"  the  spark  advance  lever  placed  in  the 
fully  retarded  position,  the  throttle  lever  set  in  the  partly  open  position, 
and  the  carburetor  " choked"  by  the  carburetor  control  button  on  the 
dash.     The  starting  switch  is  then  pushed  down  with  a  firm  unhesitating 
movement  of  the  foot  as  far  as  it  will  go.     This  permits  the  starting 
current  to  flow  through  the  electric  motor  which  rotates  the  crankshaft 
of  the  engine.     If  everything  is  in  proper  order,  the  engine  will  start  in 
from  one-half  to  two  seconds.     In  cold  weather,  however,  it  may  require 
from  five  to  ten  seconds.     After  the  engine  is  running  on  its  own  power, 
the  spark  should  be  advanced  and  the  carburetor  choke  button  gradually 
pushed  in  as  the  engine  warms  up. 

150.  Failure  of  the  Engine  to  Start. — If  the  engine  does  not  start 
within  the  time  mentioned,  something  is  wrong  and  the  foot  should  be 
removed  from  the  starting  switch.     It  would  be  useless  to  subject  the 
storage  battery  to  the  unnecessary  heavy  drain  caused  by  cranking  the 
engine  for  a  long  period.     The  engine  should  be  inspected  carefully  to 
determine  whether  the  carburetor  is  getting  gasoline  and  whether  a  spark 
is  actually  taking  place  at  the  spark  plugs  at  the  proper  time.     Faults  in 
the  ignition  system  should  be  set  right.     If  fuel  is  coming  to  the  carb- 
uretor and  still  the  engine  will  not  start,  it  may  be  because  the  engine  is 
cold  and  the  gasoline  does  not  evaporate  readily.     Heat  applied  to  the 
carburetor  or  to  the  inlet  manifold  will  help  to  vaporize  the  fuel. 

151.  Testing  the  Battery  Ignition  System. — In  the  battery  ignition 
system  the  source  of  current  is  the  battery,  either  dry  or  storage  cells. 
These  are  the  first  things  to  be  examined  in  the  event  of  a  failure  of  the 
ignition  system.     The  induction  coil  is  next  in  importance  and  should  be 
tested  in  the  manner  described  in  Chapter  IX,  providing  the  battery 
is  in  good  condition.     The  interrupter  or  timer  and  the  distributor  are 
to  be  inspected  next  and  if  found  in  good  condition,  the  condenser  should 
be  inspected  very  carefully.     A  defective  condenser  will  cause  a  great 
deal  of  trouble  in  the  ignition  system,  and  in  the  event  of  damage  should 
be  repaired  or  replaced.     A  condenser  operating  properly  will  increase 

255 


256  AUTOMOTIVE  IGNITION  SYSTEMS 

the  effectiveness  of  the  spark  produced  in  the  cylinder  about  twenty-five 
times  more  than  the  spark  produced  by  an  ignition  system  in  which  the 
condenser  is  defective.  The  resistance  unit  should  also  be  given  some 
attention  to  guard  against  its  burning  out. 

152.  Testing  the  Magneto  Ignition  System. — The  magneto  ignition 
system  contains  the  same  elements  as  the  battery  system  with  the  excep- 
tion that  in  the  magneto  the  current  is  generated  within  the  instrument 
itself  by  electromagnetic  induction  instead  of  being  supplied  by  an  external 
battery.     The  magneto  ignition  system  contains  no  resistance  unit. 
The  volume  of  the  current  depends  upon  the  speed  of  rotation  of  the 
armature  of  the  magneto  and  upon  the  strength  of  its  magnets.     Weak 
magnets  will  not  provide  sufficient  magnetic  lines  of  force  to  generate  the 
required  current.     If,  in  testing  the  magneto  ignition  system,  the  parts 
mentioned  in  the  previous  paragraph  are  found  to  be  in  good  condition, 
the  magnets  have  lost  their  strength.     They  should  be  recharged  to  their 
original  strength. 

153.  Locating  a  Misfiring  Cylinder. — Misfiring  or  " missing"  of  the 
engine  may  be  caused  by  faulty  ignition,  by  a  faulty  carburetor,  or  by 
the  valves  operating  improperly.     Missing  which  occurs  with  some  regu- 
larity may  usually  be  attributed  to  faulty  ignition  or  valve  operation. 
Very  irregular  missing  is  usually  caused  by  a  faulty  carburetor,  but  it 
may  result  from  dirty  breaker  points  or  some  other  fault  in  the  ignition 
system. 

To  detect  and  correct  faulty  ignition,  the  cylinder  at  fault  must  first 
be  located.  This  may  easily  be  done  with  the  engine  running  by  short 
circuiting  the  spark  plug  or  bridging  between  the  engine  cylinder  and 
spark  plug  terminal  with  either  a  hammer  head  or  a  wooden  handled 
screwdriver  as  shown  in  Fig.  331.  If,  in  testing  the  various  spark  plugs, 
one  is  found  which,  when  short  circuited,  does  not  affect  the  operation  of 
the  engine,  it  is  in  all  probability  the  one  at  fault.  The  trouble  may  be 
either  in  the  ignition  apparatus  or  in  the  spark  plug  itself. 

Another  convenient  method  of  locating  a  misfiring  cylinder  on  en- 
gines having  vibrating  coil  ignition,  such  as  the  Ford,  is  to  run  the  engine 
first  on  one  cylinder  and  then  on  another  by  holding  down  all  of  the  vibra- 
tors except  the  one  connected  to  the  cylinder  under  test.  The  engine 
should  run  idle  on  any  one  of  the  cylinders  and  should  show  approximately 
the  same  power  from  each. 

154.  Defective  Spark  Plugs.— The  most  common  fault  found  in  the 
spark  plug  is  carbonizing  or  sooting,  which  results  in  short  circuiting 
the  high-tension  current  so  that,  instead  of  jumping  between  the  points 
or  electrodes  of  the  plugs  in  the  combustion  chamber,  it  passes  through 
the  carbon  accumulation  directly  to  the  metallic  shell.    The  plug  should  be 
removed,  and,  if  there  is  evidence  that  it  is  short  circuited,  the  carbon 
accumulation  should  be  removed.     This  may  be  done  by  first  scraping  off 


IGNITION  TROUBLES  AND  REMEDIES  257 

the  carbon  and  then  washing  the  plug  with  gasoline  and  a  stiff  brush. 
By  inspecting  the  plug  carefully,  it  can  be  determined  whether  or  not 
the  porcelain  has  become  cracked  or  damaged  in  any  way,  and  also 
whether  the  gap  or  distance  between  the  electrodes  is  correct.  This  gap 
should  be  between  .025  to  .030  (34o  to  ^-32)  in.,  about  3  thicknesses  of 
an  ordinary  U.  S.  post  card.  If  this  gap  is  found  incorrect,  the  electrode 
that  is  attached  to  the  shell  may  be  bent  until  proper  adjustment  is 
secured.  A  worn  dime  is  an  approximate  gage  to  use  for  setting  this  gap. 

The  porcelain  of  the  plug  may  be  cracked  in  such  a  manner  that  it 
will  not  show  upon  casual  inspection,  but  it  may  be  detected  as  follows : 
If  the  plug  is  screwed  into  the  cylinder  and  some  pressure  is  brought  to 
bear  against  the  upper  part  of  the  plug  with  the  finger,  grating  or  grinding 
will  sometimes  be  heard  and  a  very  small  motion  will  be  felt.  The  high- 
tension  current  will  often  bridge  the  gap  between  the  center  electrode 
and  the  shell  through  a  crack  in  the  porcelain,  instead  of  jumping  across 
the  space  intervening  between  the  electrodes  or  points  of  the  plug.  The 
spark  plug  may  be  tested  by  removing  it  from  the  cylinder  and  laying  it 
on  the  cylinder  block.  The  engine  should  be  turned  over  by  hand  and 
observations  made  as  to  whether  a  spark  jumps  between  the  electrodes. 
The  plug  should,  of  course,  be  laid  on  the  cylinder  block  so  that  no  part 
of  the  plug,  except  the  shell,  will  touch  the  cylinder  block.  This,  however, 
is  not  a  positive  test,  since  the  spark  may  sometimes  jump  the  gap  be- 
tween the  points  of  the  plug  and  yet  be  at  fault,  owing  to  the  fact  that 
under  compression  the  resistance  is  greatly  increased  between  the  plug  elec- 
trodes. The  spark  may  jump  this  gap  in  the  open  air  and  yet  not  pass 
under  the  conditions  of  operation  in  the  cylinder. 

A  positive  test  for  the  plug  is  to  replace  it  with  one  that  is  known  to  be 
perfect.  If  the  condition  is  improved,  the  original  plug  is  unquestionably 
at  fault. 

155.  Defective  Wiring  and  Ignition  Apparatus. — If  the  plugs  are 
found  in  good  order,  and  yet  one  or  more  cylinders  continue  to  misfire, 
the  trouble  may  be  due  to  a  lack  of  secondary  current  in  the  wire  con- 
nected to  the  plug.  The  trouble  can  be  located  when  the  engine  is 
running,  or  being  cranked,  by  detaching  the  wire  from  the  plug  and  hold- 
ing the  end  about  J£  m-  to  ^m.  from  the  plug  binding  terminal  or  cylinder 
head.  If  the  secondary  current  is  being  distributed  properly  to  the 
cylinder  in  question,  a  spark  will  occur  at  the  gap.  If  there  is  no  spark 
across  the  gap  and  there  is  regular  sparking  at  the  other  plugs,  the  trouble 
is  undoubtedly  due  to  defective  high-tension  wiring,  cracked  distributor 
head,  or  poor  timer  contact. 

If  the  rubber  covering  or  insulation  on  the  spark  plug  wires  is  chafed 
or  cut  through,  allowing  the  conductor  to  touch  or  nearly  touch  any 
metal  part  of  the  car,  the  current  will  be  short  circuited  and  will  not 
jump  the  gap  in  the  plugs.  It  is  not  necessary  that  this  insulation  be 

17 


258  AUTOMOTIVE  IGNITION  SYSTEMS 

worn  down  to  the  metal  of  the  conductor.  If  a  sharp  snapping  is  heard, 
when  the  engine  is  running  under  a  heavy  pull,  it  is  evidence  of  a  short 
circuit  from  the  high-tension  conductor  to  the  metal  work.  The  fault  will 
usually  be  found  due  to  imperfect  insulation  of  the  spark  plug  wires,  or  a 
wire  loose  from  the  spark  plug  terminal.  The  only  satisfactory  remedy 
for  worn  insulation  is  to  replace  the  wiring  with  new. 

Irregular  misfiring  of  all  cylinders  may  be  due  to  defective  primary 
wiring,  discharged  battery  or  weak  magneto,  corroded  or  loose  battery 
connections,  improper  adjustment  of  vibrator  or  interrupter  contact 
points,  or  defective  condenser. 

156.  Battery  Ignition  Breaker. — A  common  cause  of  irregular  mis- 
firing, when  ignition  is  from  a  battery  high-tension  distributor  unit,  is  an 
improper  make-and-break  of  the  primary  circuit  by  the  contact  points. 
In  a  majority  of  the  various  systems  employed,  the  contact  points  are 
made  of  tungsten  and  normally  held  closed  by  spring  tension,  the  spark 
occurring  the  instant  the  primary  circuit  is  broken  by  the  cam  lobe's 
bearing  against  the  contact  arm.     The  contact  points  have  a  standard 
opening  of  .020  in.,  or  about  the  thickness  of  two  U.  S.  post  cards.     If 
found  dirty  or  uneven  and  pitted,  they  should  be  cleaned  by  passing 
between  them  a  fine  flat  file,  or  preferably  a  piece  of  No.  00  sandpaper. 

157.  Defective  Condenser. — A  defective  condenser  is  indicated  by 
serious  sparking  and  rapid  burning  of  the  interrupter  or  vibrator  contact 
points  also  by  the  inability  of  the  coil  to  produce  a  hot  secondary  spark 
when  the  primary  circuit  is  interrupted.     If  these  conditions  exist,  the 
condenser   is   probably   either   punctured    (insulation    between    tinfoil 
layers  destroyed)  or  open  circuited.     A  positive  test  and  remedy  will  be 
to  replace  the  condenser  or  unit  in  which  it  is  contained  with  another  that 
is  known  to  be  good.     If  the  condenser  is  mounted  inside  the  coil,  the 
entire  coil  usually  must  be  replaced.     When  it  is  mounted  in  the  breaker 
housing,  it  can  usually  be  replaced  without  disturbing  the  other  parts 
of . the  system.     The  action  of  a  good  condenser  results  in  intensifying  the 
secondary  current  nearly  twenty-five  times  and  preventing  an  arc  at  the 
breaker  points  when  they  are  separated. 

158.  The  Resistance  Unit. — In  many  battery  ignition  systems  a  resist- 
ance unit  is  placed  in  the  primary  circuit  to  protect  the  coil  and  battery  in 
case  the  ignition  switch  is  left  on,  and  to  aid  in  equalizing  the  intensity 
of  the  secondary  spark  at  high  and  low  engine  speeds.     In  case  this 
resistance  unit  should  be  burned  out  or  for  any  other  reason  become  open 
circuited,  the  primary  circuit  will  be  opened  and  no  current  can  be  ob- 
tained at  any  of  the  plugs.     This  resistance  unit  consists  of  a  small  coil  of 
resistance  wire  and  is  usually  placed  either  on  the  coil  or  on  the  breaker 
housing.     In  case  this  resistance  unit  should  be  burned  out  or  accidentally 
broken,  the  terminals  may  be  temporarily  short  circuited  with  a  piece  of 
wire  to  relieve  an  emergency,  but  in  all  such  cases  the  resistance  unit 


IGNITION  TROUBLES  AND  REMEDIES  259 

must  be  replaced  with  another  of  the  same  kind  as  soon  as  possible.  Con- 
tinued operation  without  it  will  result  in  serious  burning  of  the  inter- 
rupter points  and  may  cause  injury  to  the  coil  and  condenser. 

159.  Coil  Adjustments. — A  frequent  cause  of  no  current  at  the  plug 
is  due  to  coil  trouble,  especially  where  a  vibrating  coil  is  used  for  each 
cylinder.     When  the  vibrator  points  become  pitted,  out  of  line,  or  burned, 
good  contact  is  impossible.     The  tension  on  the  vibrator  spring  may  also 
become  changed,  permitting  the  coil  to  consume  too  much  or  too  little 
current. 

In  the  case  of  burned  or  pitted  points,  they  should  be  filed  flat  with 
a  thin  smooth  file,  or  preferably  a  piece  of  No.  00  sandpaper  should  be 
passed  between  them.  In  either  case,  the  points  should  be  shaped  so 
as  to  meet  each  other  squarely. 

If  it  becomes  necessary  to  adjust  the  tension  on  the  vibrators,  the 
tension  should  be  entirely  taken  off  and  gradually  increased  until  the 
engine  runs  satisfactorily  under  all  load  conditions  with  the  coil  consum- 
ing as  little  current  as  possible.  It  is  very  important  to  have  all  the  units 
adjusted  alike.  This  can  be  done  easily  after  a  little  experience.  The 
most  accurate  method  of  coil  adjustment  is  with  a  coil  current  indicator 
by  which  the  amount  of  current  consumed  is  measured.  Coils  are  built 
to  consume  about  %  to  lJ/£  amp.  when  the  system  is  operating  properly; 
consequently,  the  tension  should  be  adjusted  so  that  the  current  con- 
sumption of  each  coil  is  not  much  greater  than  this  amount. 

160.  Breakdown  of   Coil  Wiring   or  Insulation. — If   no   current   is 
obtained  in  the  secondary  circuit  of  a  coil,  when  the  vibrator  is  working 
as  it  should,  the  trouble  is  probably  due  to  either  a  broken  wire  or  punc- 
tured insulation  inside  of  the  coil.     It  sometimes  happens  that  the  bind- 
ing post  wires  become  loose  from  the  post  just  inside  of  the  coil.     If  only 
a  slight  spark  can  be  obtained,  the  insulation  on  the  inside  wire,  may  be 
broken  down,  thus  causing  a  short  circuit  of  the  current.     Obviously, 
there  is  no  remedy  but  to  replace  the  coil.     Moisture  in  the  coil  may  also 
cause  it  to  become  short  circuited.     In  this  event,  the  coil  should  be 
dried    out    thoroughly    before    it    is    put    back    into    service. 

161.  Timers. — Trouble  in  the  timer  is  usually  due  to  oil,  water,  or 
dirt  which  has  gotten  into  the  housing,  causing  either  a  short  circuit 
or  poor  contact.     This  foreign  matter  should  be  cleaned  out  in  order  to 
permit  good  service.     After  a  time,  the  contact  segments  become  worn 
and  irregular,  causing  misfiring  at  high  speed.     In  this  event,  it  will  be 
necessary  to  supply  a  new  timer. 

162.  Improper  Spark  Timing. — If  the  engine  kicks  back,  when  being 
cranked,  the  spark  is  too  far  advanced  and  should  be  retarded  so  that  it 
will  not  occur  until  the  piston  has  passed  the  dead  center.  The  tendency 
of  an  early  spark  on  starting  is  to  cause  the  engine  to  start  backward. 
Too  early  a  spark  at  low  speeds  will  make  the  engine  knock  and  will  cause 
the  car  to  jerk. 


260  AUTOMOTIVE  IGNITION  SYSTEMS 

A  retarded  spark  causes  the  engine  to  overheat  and  lose  considerable 
of  its  power.  There  is  no  advantage  in  retarding  the  spark  past  center, 
even  in  starting.  When  the  engine  is  running,  the  spark  should  be 
advanced  in  proportion  to  the  speed.  With  the  spark  control  lever  fully 
retarded,  the  interrupter  points  should  be  timed  to  open  (thus  causing 
the  spark)  when  the  respective  pistons  have  just  left  the  upper  dead 
center  at  the  end  of  their  compression  strokes. 

On  cars  equipped  with  automatic  spark  advance,  the  troubles  due  to 
early  and  late  spark  are  seldom  experienced,  providing  the  original  timing 
of  the  spark  was  correctly  made.  Preignition  from  other  causes,  how- 
ever, may  occur  with  either  type  of  spark  advance. 

163.  Dry  Batteries. — Weak  or  exhausted -batteries  are  a  common 
source  of  trouble.  If  the  batteries  are  suspected,  they  should  be  tested 
with  a  small  ammeter.  If  any  one  of  the  dry  cells  shows  less  than  8  amp., 
it  should  be  taken  out  and  replaced  with  a  new  one.  One  weak  cell  will 
interfere  greatly  with  the  operation  of  the  others  in  the  set.  Occasionally, 
a  weak  dry  cell  can  be  livened  up  temporarily  by  boring  a  small  hole 
through  the  top  and  pouring  in  a  small  quantity  of  water,  or  better  still, 
vinegar.  The  effect,  however,  is  only  temporary. 

A  dry  battery  should  always  be  kept  perfectly  dry.  If  it  becomes  wet 
on  the  outside,  there  is  a  tendency  for  it  to  be  short  circuited  and  ex- 
haust itself.  This  is  true  especially  if  water  is  spilled  on  the  top  of  the 
battery  between  the  terminals. 

164.  Storage  Batteries. — If  the  storage  battery  appears  dead,  or  shows 
lack  of  energy,  it  may  be  due  to  one  of  the  following  causes:  (a)  dis- 
charged; (6)  electrolyte  in  the  jars  too  low;  (c)  specific  gravity  of  elec- 
trolyte too  low;  (d)  plates  sulphated;  (e)  corroded  terminals;  (/) 
battery  terminal  broken  loose  from  the  plates;  or  (g)  broken  down  in- 
sulation. These  troubles  are  fully  treated  in  Chapter  II. 

If  the  same  battery  is  used  for  starting  and  also  for  ignition  and  if  it 
has  very  little  charge,  it  may  not  be  strong  enough  to  produce  a  spark 
at  the  same  time  that  the  starting  motor  is  drawing  current  to  turn  the 
engine  over.  In  this  case  the  engine  will  generally  start  when  cranked 
by  hand. 

165.  Magneto  Troubles. — If  the  ignition  trouble  has  been  located 
in  the  magneto  side  of  the  ignition  system  and  the  plugs  and  wiring  sys- 
tem have  been  found  in  good  working  order,  attention  should  be  turned 
to  the  magneto  itself.  The  distributor  plate  should  be  thoroughly 
cleaned  with  a  cloth  moistened  with  gasoline,  to  remove  any  foreign 
matter  such  as  oil  and  carbon  dust  which  may  have  collected  after  con- 
siderable use.  After  attending  to  this,  it  should  be  determined  whether  or 
not  the  magneto  is  generating  current.  This  can  be  done  by  disconnect- 
ing the  magneto  ground  wire,  after  which  either  the  magneto  spark  plug 
cables  may  be  disconnected  or  the  distributor  block  removed.  A  spark 


IGNITION  TROUBLES  AND  REMEDIES  261 

gap  is  provided  by  resting  a  screwdriver  on  the  magneto  frame,  holding 
the  point  of  it  J^  in.  to  ^  in.  from  either  the  collector  ring  or  slip  ring 
brush  terminal.  If  no  spark  appears  across  this  gap,  the  trouble  is  in 
the  magneto  itself. 

The  contact  points  may  be  pitted  or  burned  or  may  not  have  the  proper 
adjustment.  The  correct  opening  of  the  magneto  interrupter  points 
is  from  .012  to  .020  (approximately  ^54)  in.  If  they  are  set  too  close, 
excessive  arcing  will  occur  and  the  points  will  burn  and  cause  weak 
spark  at  high  speeds.  If  they  are  set  too  wide,  the  result  will  be  burning  of 
the  points  and  weak  or  no  spark  at  high  engine  speeds,  in  which  case  the 
primary  winding  does  not  have  time  to  " build  up,"  thus  decreasing  the 
strength  of  the  spark.  If  the  interrupter  points  are  found  dirty  or  badly 
pitted  and  uneven,  they  may  be  cleaned  by  passing  a  thin  flat  file  or  a 
piece  of  No.  00  sandpaper  between  them.  The  contacts  should  not  be 
filed  unless  absolutely  necessary. 

The  carbon  or  collector  brushes  may  be  dirty  or  worn.  They  should 
be  cleaned,  or,  if  badly  worn,  replaced  with  new  brushes,  making  sure 
that  each  brush  has  the  proper  spring  tension. 

It  happens  occasionally  that  the  magnets  become  weak  or  demagne- 
tized or  they  may  be  placed  on  the  magneto  in  the  wrong  position.  If 
weak  or  demagnetized,  they  should  be  remagnetized  before  being  replaced. 
Care  should  be  exercised  in  getting  the  like  poles  of  the  magnets  on  the 
same  side  of  the  magneto.  Most  magnets  are  marked  with  an  N,  indicat- 
ing the  North  pole. 

166.  Premature    Ignition. — Premature    ignition    or    preignition    is 
caused   by  particles   of  carbon,  sharp  corners,  etc.  in  the  combustion 
chamber  becoming  incandescent  from  the  heat  of  explosion  and  igniting 
the  charge  on  the  compression  stroke  before  the  spark  occurs.    Preignition 
occurs  generally  when  the  engine  is  laboring  under  a  heavy  load  at  slow 
speed,  such  as  when  going  up  a  steep  hill  on  high  gear.     Any  engine  will 
have  premature  ignition  if  it  becomes  excessively  hot  under  low  speed 
and  heavy  load,  but  the  tendency  to  preignite  is  much  more  marked 
if  the  cylinder  is  full  of  carbon  deposits.     These  carbon  deposits  should 
be   cleaned  out  as  explained  before.     Preignition  may  also  be  due  to 
improper  spark  plug  installation,  such  as  using  a  plug  which  extends 
too  far  into  the  cylinder  head  and  which  is  not  properly  cooled. 

167.  Effects  of  Faulty  Ignition  on  Engine  Operation. — Any  one  of  the 
faults  mentioned  will  produce  serious  irregularities  in  the  operation  of  the 
engine.     Complete  failure  of  the  ignition  system  renders  the  engine 
inoperative.     A  failure  of  any  one  of  the  parts  of  the  system  may  throw 
the  system  completely  out  of  operation  or  may  cause  it  to  function  irregu- 
larly.    A  bad  spark  plug  will  cause  one  cylinder  of  the  engine  to  miss 
continually,  but  a  bad  plug  is  easily  detected.     A  too  wide  or  too  narrow 
gap  in  the  plug  will  cause  the  cylinder  to  miss  at  certain  speeds  and  loads. 


262  AUTOMOTIVE  IGNITION  SYSTEMS 

Defective  insulation  in  the  wires  leading  from  the  distributor  to  the  spark 
plugs  will  cause  an  intermittent  missing  of  the  cylinder  served  by  that 
wire.  A  loose  connection  in  the  primary  circuit  will  cause  missing  in  all 
the  cylinders  at  irregular  times  and  is  apt  to  be  very  annoying,  sometimes 
causing  the  engine  to  come  to  a  complete  stop  only  to  start  up  and  run  as 
usual  when  started  again. 

A  cylinder  that  fails  to  fire  part  of  the  time  will  give  more  trouble  due 
to  excessive  carbon  and  oil  than  one  that  fires  regularly.  During  the 
strokes  in  which  no  explosion  takes  place,  the  oil  carried  up  the  cylinder 
walls  will  accumulate  in  the  combustion  space.  This  oil  will  find  its 
way  to  the  spark  plug  where  it  will  sometimes  short  circuit  the  points, 
thus  preventing  any  future  ignition.  If  the  cylinder  fires  occasionally, 
the  excess  oil  will  cause  much  smoke  and  will  deposit  much  carbon.  This 
necessitates  frequent  cleaning  of  the  spark  plugs,  removal  of  the  carbon 
from  the  cylinders,  and  grinding  of  the  valves. 

An  engine  with  missing  cylinders  will  consume  more  fuel  than  one 
firing  regularly.  The  charge  of  fuel  and  air  drawn  into  the  cylinder  and 
discharged  without  combustion  is  wasted.  In  order  to  get  the  required 
amount  of  power  from  the  engine,  the  operator  opens  the  throttle  wider, 
thus  increasing  the  amount  of  fuel  used.  This  causes  the  missing  engine 
to  be  very  uneconomical,  resulting  in  high  operating  costs. 

168.  Things  to  Remember  Regarding  Ignition. — The  proper  per- 
formance of  the  ignition  system  is  so  important  that  good  care  and 
attention  will  result  in  efficient  service.  The  following  rules  should 
be  observed. 

Don't  blame  every  engine  trouble  on  the  ignition  system.  Remember 
that  there  are  other  parts  which  may  be  in  poor  condition. 

Don't  forget  to  turn  the  ignition  switch  "ON"  before  trying  to  start 
the  engine. 

Don't  try  to  operate  the  engine  on  a  worn-out  or  nearly  discharged 
battery. 

Don't  permit  the  gap  in  the  spark  plug  to  burn  too  wide.  The  proper 
distance  is  .025  in.  to  .030  in. 

Don't  allow  the  vibrator  or  interrupter  points  to  wear  uneven. 

Keep  excess  oil  and  water  away  from  the  ignition  equipment. 

Clean  the  distributor,  once  each  thousand  miles  of  driving,  by  wiping 
with  a  rag  moistened  with  gasoline. 

Inspect  all  wiring  for  defective  insulation  once  each  season.  Replace 
all  injured  portions. 

Turn  the  ignition  switch  "OFF"  each  time  the  engine  is  stopped. 

Keep  the  interrupter  or  vibrator  points  adjusted  to  the  opening 
recommended  by  the  manufacturer. 

Keep  the  safety  gap  dry. 

Keep  the  spark  plugs  clean. 


INDEX 


Action,  storage  cell,  charge,  35 

discharge,  35 
Active  material,  28 
Adding  water  to  battery,  37 
Adjustments,     aero    airplane    magneto, 
222 

breakers  and  timers,  236 

coil,  259 

Advance,  spark,  automatic  and  manual, 
78 

and  retard,  spark,  69 
Aero  magneto,  Splitdorf,  209,  214 

airplane  type,  219 
adjustments,  222 
wiring  diagram,  221 
Aircraft  engine  ignition,  135 
Alternating  current,  15 
Ammeter,  5,  22 
Ampere-hour,  8 
Amperes,  2 
Ampere-turn,  14 
Analogy,  A\ater,  induction,  16 

hydraulic,  electric  current,  1 

hydraulic,  condenser,  58 
Attraction,  magnetic,  11 
Atwater-Kent  system,  type  CC,  84 

type  K-2,  79 
Automatic  spark  advance,  78 

Atwater-Kent,  83 

Eisemann,  185 
Automatic  switch,  89,  91 
Automotive    ignition,    requirements,    51 


B 


Bakelite,  76 

Ballast  resistor,  Westinghouse,  105 

Batteries,  ignition,  wiring,  23 

parallel,  23 

series,  23 

series-multiple,  24 

Battery  ignition  systems,  timing,  rules, 
235 

care  of,  116 

testing,  255 

timing  with  engine,  115 


Battery    ignition   systems,    typical,    73 
Atwater-Kent,  type  CC,  84 

type  K-2,  79 
Connecticut,  88 
Delco,  typical,  101 
Cadillac  Eight,  122 
Liberty  Twelve  Airplane,  136 
Oldsmobile  Eight,  121 
Packard  Twin  Six,  129 
Fierce-Arrow,  132 
North  East,  98 
Philbrin,  107 
Remy,  94 

For  U.  S.  military  truck,  98 
Wagner,  111 
Westinghouse,  vertical,  103 

type  SC,  106 
Battery,,  primary,  19 
secondary,  19 

box,  31 
.  cells,  19 
charging,  41 
covers,  30 

detailed  instructions,  charging,  42 
Edison,  25 
elements,  19 
grids,  29 
groups,  29 
jars,  30 
lead,  27 
over-filling,  46 
run-down,  causes,  49 
separators,  31 
sulphation,  44 

prevention,  44 
vent  cap,  30 
Bearings,  230 

Berling  high-tension  magneto,  190 
Bosch,  DU4  magneto,  166 
dual,  170 

NU4  magneto,  173 
type  B  magneto,  176 
Box,  battery,  31 
Break-down,  coil  wiring  and  insulation, 

259   1 
Breaker,  54,  75 

care  and  adjustment,  236 
Buckling,  battery  plates,  47 
263 


264 


INDEX 


Cables  for  ignition,  239 
Cadillac  Eight,  Delco,  122 
Capacity,  condenser,  59 

storage  batteries,  40 
Care,  battery  ignition  system,  116 

breakers,  236 

distributors,  242 

dry  cells,  25 

spark  plugs,  43 

storage  battery  ignition,  49 

timers,  236 
Cells,  19 

dry,  20 

storage,  25 
Edison,  25 
lead,  27 

action  on  discharge,  35 
cell  readings,  variation  of,  38 
Charging,  battery,  41 

detailed  instructions,  42 

rate,  42 
Circuits,  2 

parallel,  6 

resistance  of,  6 

series,  6 

resistance  of,  6 
Classification,  magneto,  143 

armature  type,  143,  147 

high-tension,  143,  146 

inductor  type,  143,  147 

low-tension,  143,  146 
Coil,  adjustments,  259 

break-down,  259 

Ford,  160 

high-tension,  53 

impregnation,  55 

induction,  53 

low-tension,  52 

testing,  245 

transformer,  146,  151 

vibrating,  64 
Compass,  magnetic,  12 

deflection,  13 
Condenser,  57,  86 

capacity  of,  59 

defective,  258 

testing,  247 

troubles,  247 
Condensite,  76 

Conditions     causing     trouble,    breakers 
&nd  Aimers,  237 


Conductors,  2 
Conduit,  241 

Connecticut  ignition  system,  88 
type  H  switch,  89 
type  K  switch,  91 
Corroded  terminals,  46 
Couplings,  magneto,  229 
Covers,  battery,  30 
Crank  arrangements,  eight-cylinder 

engine,  120 

four-cylinder  engine,  117 
six-cylinder  engine,  118 
twelve-cylinder  engine,  127 
Current,  alternating,  15 
direct,  21 

electric,  effects  of,  8 
chemical,  9 
heating,  9 
magnetic,  9 

mechanical  generation,  145 
wave  form,  shuttle  wound  armature, 

147 

armature  type  magneto,  202 

inductor  type  magneto,  202 

Cylinders,      numbering    on      4-cylinder 

engines,  117 
6-cylinder  engines,  119 
8-cylinder  engines,  120 
12-cylinder  engines,  128 


D 


Defective  condensers,  258 

spark  plugs,  256 

wiring  and  apparatus,  257 
Delco  ignition  systems,  typical,  101 

airplane  engines,  136 

Cadillac  Eight,  122 

Oldsmobile  Eight,  121 

Packard  Twin  Six,  129 

Fierce-Arrow,  132 
Depolarizing,  21 
Determination  of  polarity,  14 
Dielectric,  55 
Dimensions,    standard    spark     plug, 

63 

Direct  current  from  dry  cell,  21 
Direction,  lines  of  force,  10 

current  flow,  2 

Disintegrated  battery  plates,  47 
Distilled  water  for  batteries,  3,7,  43 
Distributor,  76 

care  of,  243 


INDEX 


265 


Dixie  magneto,  205 
Drives,  magneto,  228 
Dry  battery  troubles,  260 
Dry  cells,  20 

care  of,  25 

testing,  22 
Dual  ignition  systems,  152 

Berling,  190 

Bosch,  170 

Eisemann,  181 

Simms,  188 

Splitdorf,  low-tension,  153 


E 


Edison  storage  batteries,  25 
Effects  of  electric  current,  8 

resistance  unit  upon  ignition,  77 
Eisemann     magneto,    automatic    spark 
advance,  185 

impulse  starter,  187 

timing  to  engine,  185 

type  G-4,  176 

type  GR-4,  181 
Electrical  horsepower,  8 

potential,  2 

power,  8 

resistance,  2 
Electricity,  nature  of,  1 

use  on  automobiles,  1 
Electrolyte,  2,  33 

freezing  point,  38 

leveling  cells,  47 
Electromagnet,  14 
Electromagnetic  induction,  15 
Electromagnetism,  12 
Electromotive  force,  2 
Elements,  battery,  19,  29 
Engines,    effect    of    faulty    ignition, 
261 

failure  to  start,  255 

starting,  255 
Evaporation  from  storage  battery,  37 


Force,  lines  of,  10 

in  magneto,  144 
Ford  ignition  system,  157 

coil,  160 

magneto,  157 

timing,  160 

Forming  battery  plates,  29 
Freezing,  electrolyte,  38 

G 

Gap,  safety,  59 

Gassing,  battery,  43 

Generation  of  current,  chemical,  20 

mechanical,  145 
Gravity,  specific,  33 

low  in  one  cell,  38 
Grids,  battery,  29 
Group,  battery,  29 


II 


Heat  in  storage  battery,  38 
High-tension  coil,  53 
High-tension  magneto,  146,  161 
Berling,  190 
Bosch,  DU4,  166 
Dual,  170  • 
NU4,  173 
type  B,  176 
Eisemann,  type  G4,  176 

type  GR4,  181 
Kingston,  192 
K-W,  204 
Mea,  194 
Simms,  188 
Splitdorf  Aero,  209 

Dixie,  205 
Horsepower,  8 

Hydraulic  analogy,  condenser,  58 
electric  current,  1 
Hydrometer,  34 

variations  due  tcr  temperature.  39 


Field,  magnetic,  10 

Firing  order,  4-cy Under  engines,  117 
6-cylinder  engines,  117 
8-cylinder  engines,  119 
12-cylinder  engines,  127 

Flames,  keep  away  from  battery,  44 


Ignition  batteries,  wiring,  23 

parallel,  23 

series,  23 

series  multiple,  24 
Ignition  coil  testing,  non-vibrating,  246 

vibrating,  245 


266 


INDEX 


Ignition,  faulty,  effect  of,  261 
premature,  261 
requirements  of,  automotive  engine, 

51 
Ignition  systems,  battery,  Atwater-Kent, 

type  CC,  84 
K-2,  79 

Connecticut,  -88 
Delco  typical,  101 
Cadillac  Eight,  122 
Liberty  Twelve  airplane,  136 
Oldsmobile  Eight,  121 
Packard  Twin  Six,  129 
Fierce-Arrow,  132 
North  East,  98 
Philbrin,  107 
Remy,  94 

U.  S.  military  truck,  98 
Wagner,  101 
Westinghouse  vertical,  103 

type  SC,  106 

Ignition  systems,  battery,  testing,  255 
Ignition  systems,  dual,  152 
Berling,  190 
Bosch,  170 
Eisemann,  181 
Ford,  157 
Simms,  188          . 
Splitdorf,  low-tension,  153 
Ignition  systems,  jump-spark,  56 
non-vibrating,  56 
operation,  56 
typical,  battery,  73 
vibrating,  65 
Ignition  systems,  magneto,  high-tension, 

Berling,  190 
Bosch  DU4,  166 
dual,  170 
NU4,  173 
type  B,  176 
Eisemann,  type  G4,  176 

GR4,  181 
Kingston,  192 
K-W,  204 
Mea,  194 
Simms,  188 
Splitdorf  Aero,  209 

Dixie,  205 
Ignition  systems,  magneto,  low-tension, 

Ford,  157 
Remy,  154 
Splitdorf,  153 
Ignition,  things  to  remember,  262 


Ignition  timing,  60 

general  rules,  battery,  235 
magneto,  232 

multiple  cylinder  engines,  141 
Impregnation,  coil,  55 
Improper  spark  timing,  259 
Impulse  starter,  Eisemann,  187 

Kingston,  193 

Splitdorf,  214 
care  of,  232 
Induction,  electromagnetic,  15 

coil,  53,  64 
Inductor  type  magneto,  principle,  197 

Ford,  157 

K-W,  198 

Remy,  154 

Splitdorf  Aero,  209 

Dixie,  205 

Installation,  spark  plug,  62,  243 
Instructions,  battery  charging,.  42 
Insulation,  238 

testing,  242 
Insulators,  2 

Interrupted    primary,    low-tension  mag- 
neto, 149 

shunt,  low-tension  magneto,  150 
Interrupter,  75 

adjustment,  236 

care,  236 


Jars,  battery,  30 

Jump-spark  ignition  system,  56 

K 

Kilowatt,  8 

Kilowatt-hour,  8 

Kingston  Model  O  high-tension  magneto, 

192 

Kingston  impulse  starter,  1 93 
K-W  high-tension  inductor  magneto,  204 
master  vibrator,  67 


Law,  Ohm's,  4 

Level,  electrolyte,  in  cells,  37 
Liberty  Twelve  aircraft  ignition,  136 
Lines  of  force,  10 

around  wire  carrying  current,  13 

in  magneto,  144 
Locating  misfiring  cylinder,  256 
Low-tension  coil,  52 

magneto,  146 


INDEX 


267 


Low-tension  magneto,  Ford,  157 

Remy,  154 

Splitdorf,  153 
Lubrication  230 


M 


Magnetic  attraction,  11 
compass,  12 
field,  10,  12 
metals,  10 
poles,  10 
repulsion,  11 
Magnetism,  9 
Magneto  classification,  143 
armature  type,  143,  147 
high-tension,  143,  146 
inductor  type,  143,  147 
low-tension,  143,  146 
Magneto  couplings,  229 
Magneto  drives,  228 
Magneto,  dual,  Berling,  190 
Bosch,  170 
Eisemann,  181 
Ford,  157 
Simms,  183 

Splitdorf,  low-tension,  153 
Magneto,  high-tension,  :armature    type, 

Berling,  190 
Bosch,  170 
Eisemann,  176 
Kingston,  192 
Mea,  194 
Simms,  188 

inductor  type,  K-W,  198 
Splitdorf  Aero,  209 

Dixie,  205 

Magneto  ignition  system,  testing,  256 
Magneto,  low-tension,  Ford,  157 
interrupted  primary,  149 

shunt,  150 
Remy  inductor,  154 
Splitdorf,  153 
Magneto  timing,  general  rules,  232 

to  the  engine,  234 
Magneto  troubles,  260 
Magnets,  artificial,  10 
compound,  145 
Ford,  252 
natural,  9 
recharging,  249 
simple,  144 
Make-and-b  reak  ignition,  52 


Manual  spark  advance,  78 
Master  vibrator,  67 

K-W,  67 

Pfanstiehl,  68 
Mea  magneto,  194 

Mechanical  generation  of  current,  145 
Misfiring  cylinder,  locating,  256 
Mounting  ignition  apparatus,  225 


N 


Non-conductors,  2 
Non-electrolyte,  2 
Non-magnetic  metals,  10 
North  East  ignition  system,  98 
Numbering  cylinders,  method  of,  4-cylin- 

der,  117 
6-cylinder,  119 
8-cylinder,  120 
12-cylinder,  128 

O 

Ohm,  2 
Ohm's  Law,  4 

formula  for,  5 

Oldsmobile  Eight,  delco  system,  121 
Operation,  jump-spark  ignition  system, 

56  . 
Order  of  events,  four-stroke  cycle  engine, 

233 
Overfilling  the  battery,  effeet  of,  46 


Packard  Twin  Six,  129 
Parallel  circuits,  6 
Pfanstiehl  master  vibrator,  68 
Philbrin  ignition  system,  107 
Plates,  battery,  26,  28 

buckling  of,  47 

disintegration,  47 
Plug,  spark,  59 

location  in  cylinder,  62 

standard  dimensions  of,  63 
Plugs,  vent,  battery,  42 
Polarity  of  electromagnet,  14 
Polarization,  20 
Poles,  magnetic,  10 
Potential,  electric,  2 
Power,  8 

Premature  ignition,  261 
Primary  battery,  19 


268 


INDEX 


Primary  winding,  54 
Principles  of  ignition  timing,  69 


R 


Rain  water  for  storage  battery,  37 
Readings,  eel],  variation,  38 
Recharging  magnets,  249 

Ford,  252 
Relation   between   direction   of   current 

and  magnetic  field,  15 
Re  my  battery  ignition  system,  94 

for  U.  S.  military  trucks,  98 

inductor  type  magneto,  154 
Repulsion,  magnetic,  11 
Requirements,  aircraft  ignition,  135 

automotive  ignition,  51 
Resistance,  2 

effect  of  temperature  on,  4 

table,  3 

unit,  77,  259 

effect  on  ignition,  77 
Resistor,  ballast,  Westinghouse,  105 
Right-hand  rule,  17 


S 


Safety  gap,  59 
Secondary  battery,  19 

winding,  54 
Sediment,  48 

space,  30 
Separators,  storage  battery,  31 

rubber,  32 

wood,  31 
Series  circuits,  6 

plug  ignition,  70 
Simms  dual  magneto,  188 
Solenoid,  14 
Spark  advance  and  retard,  69 

manual  and  automatic,  78 
Spark  plugs,  care  of,  243 

cleaning,  245 

defective,  256 

installation,  62,  243 

location,  62 

standard  dimensions,  63 

testing,  244 
Spark  timing,  60 

improper,  259 
Specific  gravity,  33 

low  in  one  cell,  38 


Splitdorf  Aero  magneto,  209 

Dixie  magneto,  205 

low-tension  magneto,  153 
Starting  the  engine,  255 
Storage  battery,  25 

action,  charge,  35 
discharge,  36 

capacity,  40 

care,  winter,  49 

Edison,  25 

heat  formed  in,  36 

lead  battery,  27 

run  down,  49 

sediment,  30 

testing,  37 

troubles,  260 
Storage  cells,  25 
Sulphation,  storage  battery,  44 

prevention,  45 
Switch,  Aero,  214 

automatic,  89,  91 

Bosch,  173 

Connecticut  H,  89 
K,  91 

Dixie,  209 

Eisemann,  183 

Philbrin,  109 

Westinghouse,  105 


Temperature,    effect,  hydrometer  read- 
ings, 39 
resistance,  4 

Terminals  and  wiring.  238 
Terminals,  corrosion  of,  46 

negative,  2 

positive,  2 
Testing,  battery  ignition  system,  255 

condenser,  247 

dry  cells,  22 

high-tension  insulation,  242 

ignition  coil,  245 

magneto,  256 

spark  plugs,  244  • 

storage  battery,  37 
Three-terminal  coil,  65 
Timer,  54,  66,  259 

care  of,  236 
Timing  battery  ignition  system,  115 

eight-  and  twelve-cylinder  systems, 
141 

Ford  system,  160 


INDEX 


269 


Timing    battery    ignition    system,    im- 
proper, 259 

magneto,  general,  232 

to  engine,  234 
Transformer  coil,  146 
Troubles,  dry  battery,  260 

magneto,  260 

storage  battery,  260 
Types  of  magnets,  144 
Typical  battery  ignition  system,  73 

U 

Unit,  resistance,  77 

effect  on  ignition,  77 


Variations  inc  ell  readings,  hydrometer,  38 
Vent  caps,  battery,  30 

plugs,  battery,  42 
Vibrating  ignition  system,  65 

induction  coil,  64 
Vibrators,  master,  67 

K-W,  67 

Pfanstiehl,  68 
Volt,  2 
Voltmeter,  5 

W 

Water  analogy,  condenser,  58 
electric  current,  1 
induction,  16 
Water,  evaporation,  storage  battery,  37 

adding  to  storage  battery,  37 
Watt,  8 
Wave,  current,  shuttle  wound  armature 

magneto,  147 

inductor  type  magneto,  202 
Westinghouse  ignition  system,  vertical, 

103 
type  SC,  106 


Winding,  primary,  54 

secondary,  54 
Wires,  resistance  of,  3 
Wiring  and  terminals,  238 
Wiring  diagrams,  Atwater  Kent,  type  CC, 

86 

K-2,  82 

Berling  magneto,  192 
Bosch  dual,  172 
DU4,  166 
NU4,  175 
Connecticut  type  H,  92 

K,  93 

Delco,  typical,  103 
Cadillac  Eight,  125 
Liberty  Aircraft,  141 
Oldsmobile  Eight,  123 
Packard  Twin  Six,  129  ' 
Fierce-Arrow,  135 
Eisemann  G4,  180 

GR4,  184 
Ford,  66,  159 
K-W  magneto,  204 
low-tension     magneto,    interrupted 

primary,  149 
shunt,  151 
Philbrin,  108 
Remy  inductor  magneto,  157 

2-terminal  coil,  battery  system,  96 
3-terminal  coil,  battery  system,  97 
Simms  magneto,  189 
Splitdorf  Aero  magneto,  217 

for  airplane,  221 
Dixie  magneto,  208 
low-tension  dual,  153 
Wagner,  115 
Westinghouse  vertical,  105 

type  SC,  107 
Wiring,  high-tension,  241 
Wiring  ignition  batteries,  in  parallel,  23 
series,  23 
series  multiple,  24 


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